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JP

Joe Pucciarelli

Sat, Feb 1, 2025 9:24 PM

I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents!

Joe Pucciarelli
MARJOE
NT37-175

On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa sentoa@lists.sentoa.org wrote:

CAUTION: External Email.

The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm.

On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch.

I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html

On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa sentoa@lists.sentoa.org wrote:

Hi all, and greetings from the UK.

My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse.

Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal.

So, 2 questions:

Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?)
Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?.

Thanks all

Steve
SINBAD
NT37/192

Sentoa mailing list -- sentoa@lists.sentoa.org
To unsubscribe send an email to sentoa-leave@lists.sentoa.org

I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents! Joe Pucciarelli MARJOE NT37-175 On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa <sentoa@lists.sentoa.org> wrote: CAUTION: External Email. The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm. On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch. I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa <sentoa@lists.sentoa.org> wrote: Hi all, and greetings from the UK. My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse. Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal. So, 2 questions: - Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?) - Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?. Thanks all Steve SINBAD NT37/192 _______________________________________________ Sentoa mailing list -- sentoa@lists.sentoa.org To unsubscribe send an email to sentoa-leave@lists.sentoa.org _______________________________________________ Sentoa mailing list -- sentoa@lists.sentoa.org To unsubscribe send an email to sentoa-leave@lists.sentoa.org

HH

Harry Hungate

Sat, Feb 1, 2025 10:07 PM

One more comment on compressing the bellows on the PSS shaft seal: After compressing the bellows sufficiently to obtain dripless service, install a hose clamp around the shaft up tight against the stainless steel rotor. This will keep the rotor from creeping--not everyone gets the allen screws (grub screws to the British subjects!) sufficiently tight.
Harry Hungate

On Feb 1, 2025, at 4:25 PM, Joe Pucciarelli via Sentoa sentoa@lists.sentoa.org wrote:

I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents!

Joe Pucciarelli
MARJOE
NT37-175

On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa sentoa@lists.sentoa.org wrote:

CAUTION: External Email.

The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm.

On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch.

I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html

On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa sentoa@lists.sentoa.org wrote:

Hi all, and greetings from the UK.

My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse.

Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal.

So, 2 questions:

Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?)
Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?.

Thanks all

Steve
SINBAD
NT37/192

Sentoa mailing list -- sentoa@lists.sentoa.org
To unsubscribe send an email to sentoa-leave@lists.sentoa.org

One more comment on compressing the bellows on the PSS shaft seal: After compressing the bellows sufficiently to obtain dripless service, install a hose clamp around the shaft up tight against the stainless steel rotor. This will keep the rotor from creeping--not everyone gets the allen screws (grub screws to the British subjects!) sufficiently tight. Harry Hungate > On Feb 1, 2025, at 4:25 PM, Joe Pucciarelli via Sentoa <sentoa@lists.sentoa.org> wrote: > > > > I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents! > > Joe Pucciarelli > MARJOE > NT37-175 > >>> On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa <sentoa@lists.sentoa.org> wrote: >>> >> CAUTION: External Email. >> >> >> The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm. >> >> On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch. >> >> I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html >> >>>> On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa <sentoa@lists.sentoa.org> wrote: >>> >>> Hi all, and greetings from the UK. >>> >>> My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse. >>> >>> Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal. >>> >>> So, 2 questions: >>> - Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?) >>> - Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?. >>> >>> Thanks all >>> >>> Steve >>> SINBAD >>> NT37/192 >>> >>> _______________________________________________ >>> Sentoa mailing list -- sentoa@lists.sentoa.org >>> To unsubscribe send an email to sentoa-leave@lists.sentoa.org >> _______________________________________________ >> Sentoa mailing list -- sentoa@lists.sentoa.org >> To unsubscribe send an email to sentoa-leave@lists.sentoa.org > _______________________________________________ > Sentoa mailing list -- sentoa@lists.sentoa.org > To unsubscribe send an email to sentoa-leave@lists.sentoa.org

BM

Ben McCafferty

Sat, Feb 1, 2025 10:19 PM

Adding my $.02 also. There is a new version of the PSS (the “pro”) that is much more rigid on the boot. It is nearly impossible to get the amount of compression that they call for in their chart, especially by yourself, unless you have something with which to compress. In my case, me in the bilge pushing with both legs, and a buddy tightening the set screws.

Someone already mentioned this, but there are two set screws in each position, and they are single use only. If you take the advice to compress the stainless collar further, replace all four screws and use a drop of the loctite they give you.

Also, the pro version comes with a second stainless collar, in two halves, that gets installed forward of the main collar, after the main collar is used to compress the boot and secured. That secondary collar is to keep the main collar from working forward over time. If you have the standard version, a good hose clamp forward of the main collar can serve the same purpose.

With either version, a critical item, from my own unfortunate experience—check regularly to be sure the hose that leads to the boot is getting water flow. Some of our tugs are capable of speeds that will pull water out of the boot astern, thus starving the seal and the forward Cutless bearing of water, and causing them to fail fast.

In my case, that water line had clogged (mine is a takeoff from the gear oil cooler, and it clogged there)—but since the boat was in the water, the seal stayed full of water. Until I next hauled, and then it was dry, and I forgot to burp the seal when we went back in the water. I made it about an hour before both water and smoke were billowing into the boat, as the PSS and the front cutless bearing had both burned. Made it back through the locks and onto the hard again, and got to replace the Cutless bearings (aft was fine, but I was there so did it anyway).

Easy to check this water flow—with engine in idle, pull the hose that attaches to the boot. Water should flow in from the boot, and also in from the hose (under pressure). Replace and check again in 6 months. In my case, I’ve now added a flow indicator in the engine room, so i can glance at that and not have to pull the hose any more.

I echo others’ remarks—prop shaft needs to be straight for really any seal to work, not to mention avoiding tearing up the reduction gear…

Based on other’s experience the only downside of a Tides seal is that it will wear a groove in the prop shaft, and will need to be moved around a bit if/when replaced, etc. The PSS does not have the problem.

In my own experience now with both regular and Pro PSS, I have never had one mist/leak when properly installed and adjusted.

As to replacement of the Cutless bearings, they are widely available (Cutless is a product/brand name) and relatively easy to work with. You carefully saw through the old one from the inside so you can roll it a bit and make it smaller to come out easier. Then freeze the new one for a few hours (or whatever you can) before installation. In my case, the stern one was much harder to install, and we ended up needing a significant hammer (10#) and steel to put across it in order to get it in all the way. Both bearings will protrude about 1/2” when fully seated. Measure/mark the new ones before they go in if you’re not sure.

In my case, there were set screws (two per bearing I believe), and it took some searching to find the stern ones below 15 years of bottom paint. :)

Best of luck and ping me if I can shed any further light. OK, maybe that was more like $0.05, ha.

Ben
nessie 37-202

On Feb 1, 2025, at 13:24, Joe Pucciarelli via Sentoa sentoa@lists.sentoa.org wrote:

I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents!

Joe Pucciarelli
MARJOE
NT37-175

On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa sentoa@lists.sentoa.org wrote:

CAUTION: External Email.

The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm.

On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch.

I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html

On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa sentoa@lists.sentoa.org wrote:

Hi all, and greetings from the UK.

My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse.

Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal.

So, 2 questions:

Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?)
Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?.

Thanks all

Steve
SINBAD
NT37/192

Sentoa mailing list -- sentoa@lists.sentoa.org
To unsubscribe send an email to sentoa-leave@lists.sentoa.org

Adding my $.02 also. There is a new version of the PSS (the “pro”) that is much more rigid on the boot. It is nearly impossible to get the amount of compression that they call for in their chart, especially by yourself, unless you have something with which to compress. In my case, me in the bilge pushing with both legs, and a buddy tightening the set screws. Someone already mentioned this, but there are *two* set screws in each position, and they are single use only. If you take the advice to compress the stainless collar further, replace all four screws and use a drop of the loctite they give you. Also, the pro version comes with a second stainless collar, in two halves, that gets installed forward of the main collar, after the main collar is used to compress the boot and secured. That secondary collar is to keep the main collar from working forward over time. If you have the standard version, a good hose clamp forward of the main collar can serve the same purpose. With either version, a critical item, from my own unfortunate experience—check regularly to be sure the hose that leads to the boot is getting water flow. Some of our tugs are capable of speeds that will pull water out of the boot astern, thus starving the seal and the forward Cutless bearing of water, and causing them to fail fast. In my case, that water line had clogged (mine is a takeoff from the gear oil cooler, and it clogged there)—but since the boat was in the water, the seal stayed full of water. Until I next hauled, and then it was dry, and I forgot to burp the seal when we went back in the water. I made it about an hour before both water and smoke were billowing into the boat, as the PSS and the front cutless bearing had both burned. Made it back through the locks and onto the hard again, and got to replace the Cutless bearings (aft was fine, but I was there so did it anyway). Easy to check this water flow—with engine in idle, pull the hose that attaches to the boot. Water should flow in from the boot, and also in from the hose (under pressure). Replace and check again in 6 months. In my case, I’ve now added a flow indicator in the engine room, so i can glance at that and not have to pull the hose any more. I echo others’ remarks—prop shaft needs to be straight for really any seal to work, not to mention avoiding tearing up the reduction gear… Based on other’s experience the only downside of a Tides seal is that it will wear a groove in the prop shaft, and will need to be moved around a bit if/when replaced, etc. The PSS does not have the problem. In my own experience now with both regular and Pro PSS, I have never had one mist/leak when properly installed and adjusted. As to replacement of the Cutless bearings, they are widely available (Cutless is a product/brand name) and relatively easy to work with. You carefully saw through the old one from the inside so you can roll it a bit and make it smaller to come out easier. Then freeze the new one for a few hours (or whatever you can) before installation. In my case, the stern one was much harder to install, and we ended up needing a significant hammer (10#) and steel to put across it in order to get it in all the way. Both bearings will protrude about 1/2” when fully seated. Measure/mark the new ones before they go in if you’re not sure. In my case, there were set screws (two per bearing I believe), and it took some searching to find the stern ones below 15 years of bottom paint. :) Best of luck and ping me if I can shed any further light. OK, maybe that was more like $0.05, ha. Ben nessie 37-202 > On Feb 1, 2025, at 13:24, Joe Pucciarelli via Sentoa <sentoa@lists.sentoa.org> wrote: > > > I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents! > > Joe Pucciarelli > MARJOE > NT37-175 > >> On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa <sentoa@lists.sentoa.org> wrote: >> >> CAUTION: External Email. >> >> >> The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm. >> >> On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch. >> >> I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html >> >>> On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa <sentoa@lists.sentoa.org> wrote: >>> >>> Hi all, and greetings from the UK. >>> >>> My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse. >>> >>> Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal. >>> >>> So, 2 questions: >>> - Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?) >>> - Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?. >>> >>> Thanks all >>> >>> Steve >>> SINBAD >>> NT37/192 >>> >>> _______________________________________________ >>> Sentoa mailing list -- sentoa@lists.sentoa.org >>> To unsubscribe send an email to sentoa-leave@lists.sentoa.org >> _______________________________________________ >> Sentoa mailing list -- sentoa@lists.sentoa.org >> To unsubscribe send an email to sentoa-leave@lists.sentoa.org > _______________________________________________ > Sentoa mailing list -- sentoa@lists.sentoa.org > To unsubscribe send an email to sentoa-leave@lists.sentoa.org

FF

Fire Fighter

Sat, Feb 1, 2025 10:20 PM

Good idea Harry. PSS also sells a part made for this purpose, but a clamp is less money.
Tom

From: Harry Hungate via Sentoa sentoa@lists.sentoa.org
Sent: February 1, 2025 2:07 PM
To: sentoa@lists.sentoa.org sentoa@lists.sentoa.org
Cc: Harry Hungate wcx7106@gmail.com
Subject: [Sentoa] Re: Cutlass Bearings & shaft seals

One more comment on compressing the bellows on the PSS shaft seal: After compressing the bellows sufficiently to obtain dripless service, install a hose clamp around the shaft up tight against the stainless steel rotor. This will keep the rotor from creeping--not everyone gets the allen screws (grub screws to the British subjects!) sufficiently tight.
Harry Hungate

On Feb 1, 2025, at 4:25 PM, Joe Pucciarelli via Sentoa sentoa@lists.sentoa.org wrote:

I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents!

Joe Pucciarelli
MARJOE
NT37-175

On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa sentoa@lists.sentoa.org wrote:

CAUTION: External Email.

The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm.

On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch.

I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html

On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa sentoa@lists.sentoa.org wrote:

Hi all, and greetings from the UK.

My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse.

Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal.

So, 2 questions:

Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?)
Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?.

Thanks all

Steve
SINBAD
NT37/192

Sentoa mailing list -- sentoa@lists.sentoa.org
To unsubscribe send an email to sentoa-leave@lists.sentoa.org

Good idea Harry. PSS also sells a part made for this purpose, but a clamp is less money. Tom ________________________________ From: Harry Hungate via Sentoa <sentoa@lists.sentoa.org> Sent: February 1, 2025 2:07 PM To: sentoa@lists.sentoa.org <sentoa@lists.sentoa.org> Cc: Harry Hungate <wcx7106@gmail.com> Subject: [Sentoa] Re: Cutlass Bearings & shaft seals One more comment on compressing the bellows on the PSS shaft seal: After compressing the bellows sufficiently to obtain dripless service, install a hose clamp around the shaft up tight against the stainless steel rotor. This will keep the rotor from creeping--not everyone gets the allen screws (grub screws to the British subjects!) sufficiently tight. Harry Hungate On Feb 1, 2025, at 4:25 PM, Joe Pucciarelli via Sentoa <sentoa@lists.sentoa.org> wrote: I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents! Joe Pucciarelli MARJOE NT37-175 On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa <sentoa@lists.sentoa.org> wrote: CAUTION: External Email. The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm. On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch. I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa <sentoa@lists.sentoa.org> wrote: Hi all, and greetings from the UK. My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse. Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal. So, 2 questions: - Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?) - Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?. Thanks all Steve SINBAD NT37/192 _______________________________________________ Sentoa mailing list -- sentoa@lists.sentoa.org To unsubscribe send an email to sentoa-leave@lists.sentoa.org _______________________________________________ Sentoa mailing list -- sentoa@lists.sentoa.org To unsubscribe send an email to sentoa-leave@lists.sentoa.org _______________________________________________ Sentoa mailing list -- sentoa@lists.sentoa.org To unsubscribe send an email to sentoa-leave@lists.sentoa.org

SD

Steve Day

Sun, Feb 2, 2025 3:53 PM

Many thanks for all the replies, appreciated.

I have measured the overall length of the PSS and it is exactly as it
should be with 1'' of compression, I will compress a bit further and see
whether this improves the black misting (new set screws). I have noticed
that on tickover (600/900 rpm) there is a very slight 'wobble' felt on the
stainless steel collar, this is less than 1mm of movement, but I can't feel
any noticeable movement on the actual shaft. I'll get the alignment checked.

Due to be lifted out in the next week or so, and the decision to change
cutlass bearings and switch to lip seal or upgrade the PSS will then be
made.

Steve
SINBAD
37-192

On Sat, 1 Feb 2025 at 22:20, Fire Fighter via Sentoa <
sentoa@lists.sentoa.org> wrote:

Good idea Harry. PSS also sells a part made for this purpose, but a clamp
is less money.
Tom

From: Harry Hungate via Sentoa sentoa@lists.sentoa.org
Sent: February 1, 2025 2:07 PM
To: sentoa@lists.sentoa.org sentoa@lists.sentoa.org
Cc: Harry Hungate wcx7106@gmail.com
Subject: [Sentoa] Re: Cutlass Bearings & shaft seals

One more comment on compressing the bellows on the PSS shaft seal: After
compressing the bellows sufficiently to obtain dripless service, install a
hose clamp around the shaft up tight against the stainless steel rotor.
This will keep the rotor from creeping--not everyone gets the allen screws
(grub screws to the British subjects!) sufficiently tight.
Harry Hungate

On Feb 1, 2025, at 4:25 PM, Joe Pucciarelli via Sentoa <
sentoa@lists.sentoa.org> wrote:

I also had issues caused by a PSS seal not being properly compressed when
it was replaced. I agree with Steve that following the specs in the PSS
table should lead to a dry and clean bilge! However, it’s absolutely
imperative to use new sets screws as stated in the PSS documents!

Joe Pucciarelli
MARJOE
NT37-175

On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa <
sentoa@lists.sentoa.org> wrote:

CAUTION: External Email.

The last time I had my PSS shaft seal replaced, after a year or so, it
began to spray/leak at medium to high rpm.

On the PSS website, I found a table showing how much compression should be
put on my seal, and discovered I needed to increase the compression a full
inch.

I did so, and all spray/leakage disappeared at all rpms. Apparently the
seal was not properly compressed when it was replaced. So, you might want
to go to the website and get the compression for your seal and check it.
The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html

On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa sentoa@lists.sentoa.org
wrote:

Hi all, and greetings from the UK.

My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it
had done around 1100 hours. As far as I'm aware the cutlass bearings have
never been replaced. The boat is in salt water which can be a bit silty on
the UK east coast. No undue vibration when going forward, but a bit grumbly
in reverse.

Secondly, I have the PSS shaft seal, which I replaced like for like in
2019, whilst the seal does not leak per se, I do get the messy black mist
spray that covers the area around the seal.

So, 2 questions:

Have I gone beyond what would be a reasonable length of time / hours to
change the bearings? (Does anybody have details of suitable replacements?)
Has anybody tried using lip shaft seals (thinking Lasdrop) instead of
PSS and had totally leak free shaft and a nice clean bilge?.

Thanks all

Steve

SINBAD

NT37/192

Sentoa mailing list -- sentoa@lists.sentoa.org

To unsubscribe send an email to sentoa-leave@lists.sentoa.org

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Many thanks for all the replies, appreciated. I have measured the overall length of the PSS and it is exactly as it should be with 1'' of compression, I will compress a bit further and see whether this improves the black misting (new set screws). I have noticed that on tickover (600/900 rpm) there is a very slight 'wobble' felt on the stainless steel collar, this is less than 1mm of movement, but I can't feel any noticeable movement on the actual shaft. I'll get the alignment checked. Due to be lifted out in the next week or so, and the decision to change cutlass bearings and switch to lip seal or upgrade the PSS will then be made. Steve SINBAD 37-192 On Sat, 1 Feb 2025 at 22:20, Fire Fighter via Sentoa < sentoa@lists.sentoa.org> wrote: > Good idea Harry. PSS also sells a part made for this purpose, but a clamp > is less money. > Tom > > ------------------------------ > *From:* Harry Hungate via Sentoa <sentoa@lists.sentoa.org> > *Sent:* February 1, 2025 2:07 PM > *To:* sentoa@lists.sentoa.org <sentoa@lists.sentoa.org> > *Cc:* Harry Hungate <wcx7106@gmail.com> > *Subject:* [Sentoa] Re: Cutlass Bearings & shaft seals > > One more comment on compressing the bellows on the PSS shaft seal: After > compressing the bellows sufficiently to obtain dripless service, install a > hose clamp around the shaft up tight against the stainless steel rotor. > This will keep the rotor from creeping--not everyone gets the allen screws > (grub screws to the British subjects!) sufficiently tight. > Harry Hungate > > On Feb 1, 2025, at 4:25 PM, Joe Pucciarelli via Sentoa < > sentoa@lists.sentoa.org> wrote: > > > > I also had issues caused by a PSS seal not being properly compressed when > it was replaced. I agree with Steve that following the specs in the PSS > table should lead to a dry and clean bilge! However, it’s absolutely > imperative to use new sets screws as stated in the PSS documents! > > Joe Pucciarelli > MARJOE > NT37-175 > > On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa < > sentoa@lists.sentoa.org> wrote: > > CAUTION: External Email. > > > The last time I had my PSS shaft seal replaced, after a year or so, it > began to spray/leak at medium to high rpm. > > On the PSS website, I found a table showing how much compression should be > put on my seal, and discovered I needed to increase the compression a full > inch. > > I did so, and all spray/leakage disappeared at all rpms. Apparently the > seal was not properly compressed when it was replaced. So, you might want > to go to the website and get the compression for your seal and check it. > The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html > > On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa <sentoa@lists.sentoa.org> > wrote: > > > Hi all, and greetings from the UK. > > > My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it > had done around 1100 hours. As far as I'm aware the cutlass bearings have > never been replaced. The boat is in salt water which can be a bit silty on > the UK east coast. No undue vibration when going forward, but a bit grumbly > in reverse. > > > Secondly, I have the PSS shaft seal, which I replaced like for like in > 2019, whilst the seal does not leak per se, I do get the messy black mist > spray that covers the area around the seal. > > > So, 2 questions: > > - Have I gone beyond what would be a reasonable length of time / hours to > change the bearings? (Does anybody have details of suitable replacements?) > > - Has anybody tried using lip shaft seals (thinking Lasdrop) instead of > PSS and had totally leak free shaft and a nice clean bilge?. > > > Thanks all > > > Steve > > SINBAD > > NT37/192 > > > _______________________________________________ > > Sentoa mailing list -- sentoa@lists.sentoa.org > > To unsubscribe send an email to sentoa-leave@lists.sentoa.org > > _______________________________________________ > Sentoa mailing list -- sentoa@lists.sentoa.org > To unsubscribe send an email to sentoa-leave@lists.sentoa.org > > _______________________________________________ > Sentoa mailing list -- sentoa@lists.sentoa.org > To unsubscribe send an email to sentoa-leave@lists.sentoa.org > > _______________________________________________ > Sentoa mailing list -- sentoa@lists.sentoa.org > To unsubscribe send an email to sentoa-leave@lists.sentoa.org >

BM

Ben McCafferty

Sun, Feb 2, 2025 5:02 PM

Cool Steve!

1mm is a massive amount of wobble, and any seal will fail with that much movement. At least in my experience. Here’s a great article on prop shaft alighment—if nothing else, it should give you an idea of the tolerances you’re shooting for.

You mentioned alignment, which is what the article is about—but there’s also trueness of shaft. If you have a bow, for example, you’l be able to align perhaps, but probably not get a good seal if the bow is near the seal.

As others have mentioned, dropping the rudder and prop shaft is not a huge job, and you could then have shaft checked and prop checked, and know that you’re smooth as silk going forward. Else you’re probably chasing ghosts and will be disappointed with a new seal.

Another easy thing is to get a run out gauge (used for check endplay in crankcase bearings and the like). Clamp that up and see how much runout/bow you have in the shaft by just turning it through by hand, and you’ll have a good idea of where yo stand without tearing anything down.

I’d also have a look at your motor mounts—if they have collapsed and let the engine settle, that can introduce bow as well of course.

Best,
b

https://www.sbmar.com/articles/all-about-propeller-shaft-alignment/
All about Propeller Shaft Alignment
sbmar.com

On Feb 2, 2025, at 07:53, Steve Day via Sentoa sentoa@lists.sentoa.org wrote:

Many thanks for all the replies, appreciated.

I have measured the overall length of the PSS and it is exactly as it should be with 1'' of compression, I will compress a bit further and see whether this improves the black misting (new set screws). I have noticed that on tickover (600/900 rpm) there is a very slight 'wobble' felt on the stainless steel collar, this is less than 1mm of movement, but I can't feel any noticeable movement on the actual shaft. I'll get the alignment checked.

Due to be lifted out in the next week or so, and the decision to change cutlass bearings and switch to lip seal or upgrade the PSS will then be made.

Steve
SINBAD
37-192

On Sat, 1 Feb 2025 at 22:20, Fire Fighter via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org> wrote:

Good idea Harry. PSS also sells a part made for this purpose, but a clamp is less money.
Tom

From: Harry Hungate via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org>
Sent: February 1, 2025 2:07 PM
To: sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org>
Cc: Harry Hungate <wcx7106@gmail.com mailto:wcx7106@gmail.com>
Subject: [Sentoa] Re: Cutlass Bearings & shaft seals

One more comment on compressing the bellows on the PSS shaft seal: After compressing the bellows sufficiently to obtain dripless service, install a hose clamp around the shaft up tight against the stainless steel rotor. This will keep the rotor from creeping--not everyone gets the allen screws (grub screws to the British subjects!) sufficiently tight.
Harry Hungate

On Feb 1, 2025, at 4:25 PM, Joe Pucciarelli via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org> wrote:

I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents!

Joe Pucciarelli
MARJOE
NT37-175

On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org> wrote:

CAUTION: External Email.

The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm.

On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch.

I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html

On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org> wrote:

Hi all, and greetings from the UK.

My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse.

Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal.

So, 2 questions:

Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?)
Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?.

Thanks all

Steve
SINBAD
NT37/192

Sentoa mailing list -- sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org
To unsubscribe send an email to sentoa-leave@lists.sentoa.org mailto:sentoa-leave@lists.sentoa.org

Sentoa mailing list -- sentoa@lists.sentoa.org
To unsubscribe send an email to sentoa-leave@lists.sentoa.org

Cool Steve! 1mm is a massive amount of wobble, and any seal will fail with that much movement. At least in my experience. Here’s a great article on prop shaft alighment—if nothing else, it should give you an idea of the tolerances you’re shooting for. You mentioned alignment, which is what the article is about—but there’s also trueness of shaft. If you have a bow, for example, you’l be able to align perhaps, but probably not get a good seal if the bow is near the seal. As others have mentioned, dropping the rudder and prop shaft is not a huge job, and you could then have shaft checked and prop checked, and know that you’re smooth as silk going forward. Else you’re probably chasing ghosts and will be disappointed with a new seal. Another easy thing is to get a run out gauge (used for check endplay in crankcase bearings and the like). Clamp that up and see how much runout/bow you have in the shaft by just turning it through by hand, and you’ll have a good idea of where yo stand without tearing anything down. I’d also have a look at your motor mounts—if they have collapsed and let the engine settle, that can introduce bow as well of course. Best, b https://www.sbmar.com/articles/all-about-propeller-shaft-alignment/ All about Propeller Shaft Alignment sbmar.com > On Feb 2, 2025, at 07:53, Steve Day via Sentoa <sentoa@lists.sentoa.org> wrote: > > Many thanks for all the replies, appreciated. > > I have measured the overall length of the PSS and it is exactly as it should be with 1'' of compression, I will compress a bit further and see whether this improves the black misting (new set screws). I have noticed that on tickover (600/900 rpm) there is a very slight 'wobble' felt on the stainless steel collar, this is less than 1mm of movement, but I can't feel any noticeable movement on the actual shaft. I'll get the alignment checked. > > Due to be lifted out in the next week or so, and the decision to change cutlass bearings and switch to lip seal or upgrade the PSS will then be made. > > Steve > SINBAD > 37-192 > > On Sat, 1 Feb 2025 at 22:20, Fire Fighter via Sentoa <sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org>> wrote: >> Good idea Harry. PSS also sells a part made for this purpose, but a clamp is less money. >> Tom >> >> From: Harry Hungate via Sentoa <sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org>> >> Sent: February 1, 2025 2:07 PM >> To: sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org> <sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org>> >> Cc: Harry Hungate <wcx7106@gmail.com <mailto:wcx7106@gmail.com>> >> Subject: [Sentoa] Re: Cutlass Bearings & shaft seals >> >> One more comment on compressing the bellows on the PSS shaft seal: After compressing the bellows sufficiently to obtain dripless service, install a hose clamp around the shaft up tight against the stainless steel rotor. This will keep the rotor from creeping--not everyone gets the allen screws (grub screws to the British subjects!) sufficiently tight. >> Harry Hungate >> >>> On Feb 1, 2025, at 4:25 PM, Joe Pucciarelli via Sentoa <sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org>> wrote: >>> >>> >>> >>> I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents! >>> >>> Joe Pucciarelli >>> MARJOE >>> NT37-175 >>> >>>> On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa <sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org>> wrote: >>>> >>>> CAUTION: External Email. >>>> >>>> >>>> The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm. >>>> >>>> On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch. >>>> >>>> I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html >>>> >>>>> On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa <sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org>> wrote: >>>>> >>>>> Hi all, and greetings from the UK. >>>>> >>>>> My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse. >>>>> >>>>> Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal. >>>>> >>>>> So, 2 questions: >>>>> - Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?) >>>>> - Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?. >>>>> >>>>> Thanks all >>>>> >>>>> Steve >>>>> SINBAD >>>>> NT37/192 >>>>> >>>>> _______________________________________________ >>>>> Sentoa mailing list -- sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org> >>>>> To unsubscribe send an email to sentoa-leave@lists.sentoa.org <mailto:sentoa-leave@lists.sentoa.org> >>>> _______________________________________________ >>>> Sentoa mailing list -- sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org> >>>> To unsubscribe send an email to sentoa-leave@lists.sentoa.org <mailto:sentoa-leave@lists.sentoa.org> >>> _______________________________________________ >>> Sentoa mailing list -- sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org> >>> To unsubscribe send an email to sentoa-leave@lists.sentoa.org <mailto:sentoa-leave@lists.sentoa.org> >> _______________________________________________ >> Sentoa mailing list -- sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org> >> To unsubscribe send an email to sentoa-leave@lists.sentoa.org <mailto:sentoa-leave@lists.sentoa.org> > _______________________________________________ > Sentoa mailing list -- sentoa@lists.sentoa.org > To unsubscribe send an email to sentoa-leave@lists.sentoa.org

G

gefuller5@comcast.net

Sun, Feb 2, 2025 8:19 PM

The Jack Harden article found on the Seaboard Marine website is quite complete, but it is overly complex for the vast majority of cases. (The Seaboard section is mostly about initial alignment in a new installation, not routine maintenance.)

The Harden article spends a lot of time trying to find the best rotational fit between the transmisison flange and the shaft coupling. Yes, that is important. However, I have never found a transmission coupling that was not flat and perpendicular to the rotation to better than 0.001 inches.

The rest of the article is good, but the multiple measurements to find the best fit is a bit of overkill.

The entire process is quite doable without spreadsheets for the ordinary careful boat owner who is somewhat conversant with tools and such.

Gene Fuller

Yorkshire Rose

NT 37136

Punta Gorda, FL

The Jack Harden article found on the Seaboard Marine website is quite complete, but it is overly complex for the vast majority of cases. (The Seaboard section is mostly about initial alignment in a new installation, not routine maintenance.) The Harden article spends a lot of time trying to find the best rotational fit between the transmisison flange and the shaft coupling. Yes, that is important. However, I have never found a transmission coupling that was not flat and perpendicular to the rotation to better than 0.001 inches. The rest of the article is good, but the multiple measurements to find the best fit is a bit of overkill. The entire process is quite doable without spreadsheets for the ordinary careful boat owner who is somewhat conversant with tools and such. Gene Fuller *Yorkshire Rose* NT 37136 Punta Gorda, FL

BM

Ben McCafferty

Mon, Feb 3, 2025 5:06 PM

I hear you Gene.

My intent with that article, within the context of the prop shaft seal conversation, was to show the OP some of the ways the runout at the seal can happen and cause a leak. Alignment might or might not help, depending on where his problem lies. Specifically, bow in the shaft (either because it’s bent or because engine mounts have failed and caused a bow from sagging) could cause his described symptoms and original problem.

As to the article on its own termas--I have used the method described very successfully, but just used a note pad and pen to record the various measurements—no spreadsheets (and I love spreadsheets!). :) While thorough, there are no extra measurements taken—just every possible orientation—and then the average of those gives the best end result. I was able to do this process, by myself, in about 20-30 minutes on the hard. It’s possible in the water, but harder to turn the prop shaft through.

That said, the yard guys who have done this for me in the past have also used a different system altogether, with great results. They do use feeler gauges, but not as many measurements. A bit more “seat of the pants”, but with 20 years’ experience, they got a great result also. For me, as a skilled wrench but not heavily experienced with alignment, the article gave a methodical and repeatable way to approach the problem.

Take good care and see you on the water!
b

On Feb 2, 2025, at 12:19, Gene Fuller via Sentoa sentoa@lists.sentoa.org wrote:

The Jack Harden article found on the Seaboard Marine website is quite complete, but it is overly complex for the vast majority of cases. (The Seaboard section is mostly about initial alignment in a new installation, not routine maintenance.)

The Harden article spends a lot of time trying to find the best rotational fit between the transmisison flange and the shaft coupling. Yes, that is important. However, I have never found a transmission coupling that was not flat and perpendicular to the rotation to better than 0.001 inches.

The rest of the article is good, but the multiple measurements to find the best fit is a bit of overkill.

The entire process is quite doable without spreadsheets for the ordinary careful boat owner who is somewhat conversant with tools and such.

Gene Fuller

Yorkshire Rose

NT 37136

Punta Gorda, FL

Sentoa mailing list -- sentoa@lists.sentoa.org
To unsubscribe send an email to sentoa-leave@lists.sentoa.org

I hear you Gene. My intent with that article, within the context of the prop shaft seal conversation, was to show the OP some of the ways the runout at the seal can happen and cause a leak. Alignment might or might not help, depending on where his problem lies. Specifically, bow in the shaft (either because it’s bent or because engine mounts have failed and caused a bow from sagging) could cause his described symptoms and original problem. As to the article on its own termas--I have used the method described very successfully, but just used a note pad and pen to record the various measurements—no spreadsheets (and I love spreadsheets!). :) While thorough, there are no extra measurements taken—just every possible orientation—and then the average of those gives the best end result. I was able to do this process, by myself, in about 20-30 minutes on the hard. It’s possible in the water, but harder to turn the prop shaft through. That said, the yard guys who have done this for me in the past have also used a different system altogether, with great results. They do use feeler gauges, but not as many measurements. A bit more “seat of the pants”, but with 20 years’ experience, they got a great result also. For me, as a skilled wrench but not heavily experienced with alignment, the article gave a methodical and repeatable way to approach the problem. Take good care and see you on the water! b > On Feb 2, 2025, at 12:19, Gene Fuller via Sentoa <sentoa@lists.sentoa.org> wrote: > > The Jack Harden article found on the Seaboard Marine website is quite complete, but it is overly complex for the vast majority of cases. (The Seaboard section is mostly about initial alignment in a new installation, not routine maintenance.) > > The Harden article spends a lot of time trying to find the best rotational fit between the transmisison flange and the shaft coupling. Yes, that is important. However, I have never found a transmission coupling that was not flat and perpendicular to the rotation to better than 0.001 inches. > > The rest of the article is good, but the multiple measurements to find the best fit is a bit of overkill. > > The entire process is quite doable without spreadsheets for the ordinary careful boat owner who is somewhat conversant with tools and such. > > Gene Fuller > > Yorkshire Rose > > NT 37136 > > Punta Gorda, FL > > _______________________________________________ > Sentoa mailing list -- sentoa@lists.sentoa.org > To unsubscribe send an email to sentoa-leave@lists.sentoa.org

KB

Kelly Britz

Fri, Feb 7, 2025 7:02 PM

To add to this great post: I managed to track down specific maximum cutlass bearing wear along with other useful details on keeping the bearings healthy.
Duramax is the manufacturer of the cutlass bearing NT installs on at least the 37, 39, & 40's and also NT’s recommended source for replacement bearings. Duramax’s Tom Farkas (West Coast Sales, Marine) sent me detailed Duramax and US Navy materials on cutlass bearing lubrication/operation theory and various shaft clearance parameters.
Here are my take-aways from this material specific to a 2” NT37/39/40 propeller shaft:

New shaft-bearing clearance: Duramax P/N 870512100/”CALL” is the 2”IDx8”long nitrile rubber lined naval brass cutlass bearing for a 2” shaft, has an original manufactured ID of 2.006”-2.012” out of the box.
*
Running clearance: US Navy/NSTM “Minimum Operating clearance of bearings” (I assume after break-in) 0.017” clearance for a 2” shaft.
*
Max wear clearance: US Navy/NSTM “Total Clearance at which bearing should be renewed” for a 2” shaft is 0.091” (at ~3/32", that would certainly be visible and quite likely ‘thunk’ when lifting the prop and shaft!).

Wear factors: “Duramax Factors That Affect Cutlass Bearing Wear”
* Load
* Rubbing velocity
* Time at 0 velocity
- (suggests if vessel idle > 1 week, shaft should be rotated 450 degrees weekly)
  * Uniformity of loading
- (I assume this includes all shaft alignment issues)
  * Velocity time interaction
  * Shaft and bearing roughness
  * Shaft and bearing combination
  * Water quality and contamination
  * Raw Water Temperature
- Raw water lubrication temperature should be as close to ambient sea water temp as possible
- Raw water feed connection should occur before heat exchanger
Raw water flow requirements: Duramax recommended raw water flow to the cutlass bearing should be 4 gpm for a 2” shaft, more is better.
Raw water pressure requirements: PYI Inc, says 10 psi of raw water pressure for their PSS Dripless Shaft Seal.

Additional material that Tom Farkas provided included a technical paper titled “Water Lubricated Rubber Bearings, the Principles of Design and Operation” by Michael Brakey.
Included in this paper was the following quote that likely addresses some of Steve Day/SINBAD’s silty raw water lubrication concerns:
“When a grain of sand is trapped between the shaft and the rubber, it is depressed into the softer material and rolled into an adjacent water groove where it is immediately flushed out of the bearing. With proper loading, rotational speed and clearance, the shaft will ride on a thin film or wedge of water. When the shaft actually lifts itself off the rubber lands and rides a water wedge, we have what is known as hydrodynamic lubrication. At this juncture both friction and wear decrease significantly.”
This M.Brakey paper goes on with several pages of detailed theory and calculations about bearing loading, shaft velocity, and thermal expansion in the determination of proper bearing-shaft clearances for water lubricated rubber bearings.
When I get a chance, I will combine all this detailed original material from Tom Farkas / Duramax / PYI that I’ve merely summarized here, then post it together to SENTOA/Maintenance so that it will be easier for others to find down the road.
It’s great to finally know more about our cutlass bearing parameters. SANDPIPER is now at 12,800 engine hours on the original cutlass bearings and we've been measuring 0.021-0.023” of shaft play and wondering where we stand.
Thank you Ben McCafferty, I will be adding a little in-line flow indicator on the raw water shaft seal/cutlass line and will attempt to measure pressure/flow rate before we go into the yard in April.
Good luck to Steve Day, I hope you get good news in the yard this week there in the UK! Please report back.
Regards, Kelly Britz
Sandpiper, NT37-042, 2001
Edmonds/Seattle WA

From: Steve Day via Sentoa sentoa@lists.sentoa.org
Sent: Sunday, February 2, 2025 7:53 AM
To: South East Nordic Tugs Owners' Association (SENTOA) sentoa@lists.sentoa.org
Cc: Steve Day s.day2905@gmail.com
Subject: [Sentoa] Re: Cutlass Bearings & shaft seals

Many thanks for all the replies, appreciated.

I have measured the overall length of the PSS and it is exactly as it should be with 1'' of compression, I will compress a bit further and see whether this improves the black misting (new set screws). I have noticed that on tickover (600/900 rpm) there is a very slight 'wobble' felt on the stainless steel collar, this is less than 1mm of movement, but I can't feel any noticeable movement on the actual shaft. I'll get the alignment checked.

Due to be lifted out in the next week or so, and the decision to change cutlass bearings and switch to lip seal or upgrade the PSS will then be made.

Steve
SINBAD
37-192

On Sat, 1 Feb 2025 at 22:20, Fire Fighter via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org> wrote:
Good idea Harry. PSS also sells a part made for this purpose, but a clamp is less money.
Tom

From: Harry Hungate via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org>
Sent: February 1, 2025 2:07 PM
To: sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org>
Cc: Harry Hungate <wcx7106@gmail.com mailto:wcx7106@gmail.com>
Subject: [Sentoa] Re: Cutlass Bearings & shaft seals

One more comment on compressing the bellows on the PSS shaft seal: After compressing the bellows sufficiently to obtain dripless service, install a hose clamp around the shaft up tight against the stainless steel rotor. This will keep the rotor from creeping--not everyone gets the allen screws (grub screws to the British subjects!) sufficiently tight.
Harry Hungate

On Feb 1, 2025, at 4:25 PM, Joe Pucciarelli via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org> wrote:

I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents!

Joe Pucciarelli
MARJOE
NT37-175

On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org> wrote:

CAUTION: External Email.

The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm.

On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch.

I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html

On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org> wrote:

Hi all, and greetings from the UK.

My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse.

Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal.

So, 2 questions:

Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?)
Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?.

Thanks all

Steve
SINBAD
NT37/192

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To add to this great post: I managed to track down specific maximum cutlass bearing wear along with other useful details on keeping the bearings healthy. Duramax is the manufacturer of the cutlass bearing NT installs on at least the 37, 39, & 40's and also NT’s recommended source for replacement bearings. Duramax’s Tom Farkas (West Coast Sales, Marine) sent me detailed Duramax and US Navy materials on cutlass bearing lubrication/operation theory and various shaft clearance parameters. Here are my take-aways from this material specific to a 2” NT37/39/40 propeller shaft: * New shaft-bearing clearance: Duramax P/N 870512100/”CALL” is the 2”IDx8”long nitrile rubber lined naval brass cutlass bearing for a 2” shaft, has an original manufactured ID of 2.006”-2.012” out of the box. * Running clearance: US Navy/NSTM “Minimum Operating clearance of bearings” (I assume after break-in) 0.017” clearance for a 2” shaft. * Max wear clearance: US Navy/NSTM “Total Clearance at which bearing should be renewed” for a 2” shaft is 0.091” (at ~3/32", that would certainly be visible and quite likely ‘thunk’ when lifting the prop and shaft!). * Wear factors: “Duramax Factors That Affect Cutlass Bearing Wear” * Load * Rubbing velocity * Time at 0 velocity * (suggests if vessel idle > 1 week, shaft should be rotated 450 degrees weekly) * Uniformity of loading * (I assume this includes all shaft alignment issues) * Velocity time interaction * Shaft and bearing roughness * Shaft and bearing combination * Water quality and contamination * Raw Water Temperature * Raw water lubrication temperature should be as close to ambient sea water temp as possible * Raw water feed connection should occur before heat exchanger * Raw water flow requirements: Duramax recommended raw water flow to the cutlass bearing should be 4 gpm for a 2” shaft, more is better. * Raw water pressure requirements: PYI Inc, says 10 psi of raw water pressure for their PSS Dripless Shaft Seal. Additional material that Tom Farkas provided included a technical paper titled “Water Lubricated Rubber Bearings, the Principles of Design and Operation” by Michael Brakey. Included in this paper was the following quote that likely addresses some of Steve Day/SINBAD’s silty raw water lubrication concerns: “When a grain of sand is trapped between the shaft and the rubber, it is depressed into the softer material and rolled into an adjacent water groove where it is immediately flushed out of the bearing. With proper loading, rotational speed and clearance, the shaft will ride on a thin film or wedge of water. When the shaft actually lifts itself off the rubber lands and rides a water wedge, we have what is known as hydrodynamic lubrication. At this juncture both friction and wear decrease significantly.” This M.Brakey paper goes on with several pages of detailed theory and calculations about bearing loading, shaft velocity, and thermal expansion in the determination of proper bearing-shaft clearances for water lubricated rubber bearings. When I get a chance, I will combine all this detailed original material from Tom Farkas / Duramax / PYI that I’ve merely summarized here, then post it together to SENTOA/Maintenance so that it will be easier for others to find down the road. It’s great to finally know more about our cutlass bearing parameters. SANDPIPER is now at 12,800 engine hours on the original cutlass bearings and we've been measuring 0.021-0.023” of shaft play and wondering where we stand. Thank you Ben McCafferty, I will be adding a little in-line flow indicator on the raw water shaft seal/cutlass line and will attempt to measure pressure/flow rate before we go into the yard in April. Good luck to Steve Day, I hope you get good news in the yard this week there in the UK! Please report back. Regards, Kelly Britz Sandpiper, NT37-042, 2001 Edmonds/Seattle WA ________________________________ From: Steve Day via Sentoa <sentoa@lists.sentoa.org> Sent: Sunday, February 2, 2025 7:53 AM To: South East Nordic Tugs Owners' Association (SENTOA) <sentoa@lists.sentoa.org> Cc: Steve Day <s.day2905@gmail.com> Subject: [Sentoa] Re: Cutlass Bearings & shaft seals Many thanks for all the replies, appreciated. I have measured the overall length of the PSS and it is exactly as it should be with 1'' of compression, I will compress a bit further and see whether this improves the black misting (new set screws). I have noticed that on tickover (600/900 rpm) there is a very slight 'wobble' felt on the stainless steel collar, this is less than 1mm of movement, but I can't feel any noticeable movement on the actual shaft. I'll get the alignment checked. Due to be lifted out in the next week or so, and the decision to change cutlass bearings and switch to lip seal or upgrade the PSS will then be made. Steve SINBAD 37-192 On Sat, 1 Feb 2025 at 22:20, Fire Fighter via Sentoa <sentoa@lists.sentoa.org<mailto:sentoa@lists.sentoa.org>> wrote: Good idea Harry. PSS also sells a part made for this purpose, but a clamp is less money. Tom ________________________________ From: Harry Hungate via Sentoa <sentoa@lists.sentoa.org<mailto:sentoa@lists.sentoa.org>> Sent: February 1, 2025 2:07 PM To: sentoa@lists.sentoa.org<mailto:sentoa@lists.sentoa.org> <sentoa@lists.sentoa.org<mailto:sentoa@lists.sentoa.org>> Cc: Harry Hungate <wcx7106@gmail.com<mailto:wcx7106@gmail.com>> Subject: [Sentoa] Re: Cutlass Bearings & shaft seals One more comment on compressing the bellows on the PSS shaft seal: After compressing the bellows sufficiently to obtain dripless service, install a hose clamp around the shaft up tight against the stainless steel rotor. This will keep the rotor from creeping--not everyone gets the allen screws (grub screws to the British subjects!) sufficiently tight. Harry Hungate On Feb 1, 2025, at 4:25 PM, Joe Pucciarelli via Sentoa <sentoa@lists.sentoa.org<mailto:sentoa@lists.sentoa.org>> wrote: I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents! Joe Pucciarelli MARJOE NT37-175 On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa <sentoa@lists.sentoa.org<mailto:sentoa@lists.sentoa.org>> wrote: CAUTION: External Email. The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm. On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch. I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa <sentoa@lists.sentoa.org<mailto:sentoa@lists.sentoa.org>> wrote: Hi all, and greetings from the UK. My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse. Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal. So, 2 questions: - Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?) - Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?. Thanks all Steve SINBAD NT37/192 _______________________________________________ Sentoa mailing list -- sentoa@lists.sentoa.org<mailto:sentoa@lists.sentoa.org> To unsubscribe send an email to sentoa-leave@lists.sentoa.org<mailto:sentoa-leave@lists.sentoa.org> _______________________________________________ Sentoa mailing list -- sentoa@lists.sentoa.org<mailto:sentoa@lists.sentoa.org> To unsubscribe send an email to sentoa-leave@lists.sentoa.org<mailto:sentoa-leave@lists.sentoa.org> _______________________________________________ Sentoa mailing list -- sentoa@lists.sentoa.org<mailto:sentoa@lists.sentoa.org> To unsubscribe send an email to sentoa-leave@lists.sentoa.org<mailto:sentoa-leave@lists.sentoa.org> _______________________________________________ Sentoa mailing list -- sentoa@lists.sentoa.org<mailto:sentoa@lists.sentoa.org> To unsubscribe send an email to sentoa-leave@lists.sentoa.org<mailto:sentoa-leave@lists.sentoa.org>

BM

Ben McCafferty

Fri, Feb 7, 2025 9:09 PM

Hey Kelly!
Wow, that’s a ton of great info, thanks for adding that for the archives!

A couple of minor additions for posterity:

Our cutlass bearings (the generic noun) are also Cutless bearings (the specific brand name, incorrect spelling intentional and a trademark).

Duramax is also sometimes seen as Johnson or Johnson Duramax—same thing, especially if called “Cutless” as per above.

Lastly, I’m curious/pondering the 4gpm of recommended flow to the cutlass bearings, and 10psi for the PSS. Since the PSS can be used on a slow boat with no pressurized water feed—just with a snorkel from the pss barb—in theory, the water floods into the log/stern tube from the back when you burp the seal at launch (or automatically if you have the snorkel setup with no pressurized raw water source). In that case, it seems intuitively like the cooling/lubricating water would never be exchanged, since there would never be enough velocity to create a venturi (I think that’s the correct word) and suck water out. Perhaps this is another reason nordic tugs opted for the pressurized source? But it does make me wonder about boats with no pressure feed.

In the case of a sailboat, for example, the cutlass bearing could be fed with water from the front as it was underway; not the case on our boats.

Any thoughts on that? It’s neither here nor there, just a curiosity point for me at the moment.

Cheers for the great post!
b

On Feb 7, 2025, at 12:02, Kelly Britz via Sentoa sentoa@lists.sentoa.org wrote:

To add to this great post: I managed to track down specific maximum cutlass bearing wear along with other useful details on keeping the bearings healthy.
Duramax is the manufacturer of the cutlass bearing NT installs on at least the 37, 39, & 40's and also NT’s recommended source for replacement bearings. Duramax’s Tom Farkas (West Coast Sales, Marine) sent me detailed Duramax and US Navy materials on cutlass bearing lubrication/operation theory and various shaft clearance parameters.
Here are my take-aways from this material specific to a 2” NT37/39/40 propeller shaft:
New shaft-bearing clearance: Duramax P/N 870512100/”CALL” is the 2”IDx8”long nitrile rubber lined naval brass cutlass bearing for a 2” shaft, has an original manufactured ID of 2.006”-2.012” out of the box.
Running clearance: US Navy/NSTM “Minimum Operating clearance of bearings” (I assume after break-in) 0.017” clearance for a 2” shaft.
Max wear clearance: US Navy/NSTM “Total Clearance at which bearing should be renewed” for a 2” shaft is 0.091” (at ~3/32", that would certainly be visible and quite likely ‘thunk’ when lifting the prop and shaft!).
Wear factors: “Duramax Factors That Affect Cutlass Bearing Wear”
Load
Rubbing velocity
Time at 0 velocity
(suggests if vessel idle > 1 week, shaft should be rotated 450 degrees weekly)
Uniformity of loading
(I assume this includes all shaft alignment issues)
Velocity time interaction
Shaft and bearing roughness
Shaft and bearing combination
Water quality and contamination
Raw Water Temperature
Raw water lubrication temperature should be as close to ambient sea water temp as possible
Raw water feed connection should occur before heat exchanger
Raw water flow requirements: Duramax recommended raw water flow to the cutlass bearing should be 4 gpm for a 2” shaft, more is better.
Raw water pressure requirements: PYI Inc, says 10 psi of raw water pressure for their PSS Dripless Shaft Seal.
Additional material that Tom Farkas provided included a technical paper titled “Water Lubricated Rubber Bearings, the Principles of Design and Operation” by Michael Brakey.
Included in this paper was the following quote that likely addresses some of Steve Day/SINBAD’s silty raw water lubrication concerns:
“When a grain of sand is trapped between the shaft and the rubber, it is depressed into the softer material and rolled into an adjacent water groove where it is immediately flushed out of the bearing. With proper loading, rotational speed and clearance, the shaft will ride on a thin film or wedge of water. When the shaft actually lifts itself off the rubber lands and rides a water wedge, we have what is known as hydrodynamic lubrication. At this juncture both friction and wear decrease significantly.”
This M.Brakey paper goes on with several pages of detailed theory and calculations about bearing loading, shaft velocity, and thermal expansion in the determination of proper bearing-shaft clearances for water lubricated rubber bearings.
When I get a chance, I will combine all this detailed original material from Tom Farkas / Duramax / PYI that I’ve merely summarized here, then post it together to SENTOA/Maintenance so that it will be easier for others to find down the road.
It’s great to finally know more about our cutlass bearing parameters. SANDPIPER is now at 12,800 engine hours on the original cutlass bearings and we've been measuring 0.021-0.023” of shaft play and wondering where we stand.
Thank you Ben McCafferty, I will be adding a little in-line flow indicator on the raw water shaft seal/cutlass line and will attempt to measure pressure/flow rate before we go into the yard in April.
Good luck to Steve Day, I hope you get good news in the yard this week there in the UK! Please report back.
Regards, Kelly Britz
Sandpiper, NT37-042, 2001
Edmonds/Seattle WA

From: Steve Day via Sentoa sentoa@lists.sentoa.org
Sent: Sunday, February 2, 2025 7:53 AM
To: South East Nordic Tugs Owners' Association (SENTOA) sentoa@lists.sentoa.org
Cc: Steve Day s.day2905@gmail.com
Subject: [Sentoa] Re: Cutlass Bearings & shaft seals

Many thanks for all the replies, appreciated.

I have measured the overall length of the PSS and it is exactly as it should be with 1'' of compression, I will compress a bit further and see whether this improves the black misting (new set screws). I have noticed that on tickover (600/900 rpm) there is a very slight 'wobble' felt on the stainless steel collar, this is less than 1mm of movement, but I can't feel any noticeable movement on the actual shaft. I'll get the alignment checked.

Due to be lifted out in the next week or so, and the decision to change cutlass bearings and switch to lip seal or upgrade the PSS will then be made.

Steve
SINBAD
37-192

On Sat, 1 Feb 2025 at 22:20, Fire Fighter via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org> wrote:
Good idea Harry. PSS also sells a part made for this purpose, but a clamp is less money.
Tom

From: Harry Hungate via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org>
Sent: February 1, 2025 2:07 PM
To: sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org>
Cc: Harry Hungate <wcx7106@gmail.com mailto:wcx7106@gmail.com>
Subject: [Sentoa] Re: Cutlass Bearings & shaft seals

One more comment on compressing the bellows on the PSS shaft seal: After compressing the bellows sufficiently to obtain dripless service, install a hose clamp around the shaft up tight against the stainless steel rotor. This will keep the rotor from creeping--not everyone gets the allen screws (grub screws to the British subjects!) sufficiently tight.
Harry Hungate

On Feb 1, 2025, at 4:25 PM, Joe Pucciarelli via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org> wrote:

I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents!

Joe Pucciarelli
MARJOE
NT37-175

On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org> wrote:

CAUTION: External Email.

The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm.

On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch.

I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html

On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa <sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org> wrote:

Hi all, and greetings from the UK.

My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse.

Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal.

So, 2 questions:

Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?)
Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?.

Thanks all

Steve
SINBAD
NT37/192

Sentoa mailing list -- sentoa@lists.sentoa.org mailto:sentoa@lists.sentoa.org
To unsubscribe send an email to sentoa-leave@lists.sentoa.org mailto:sentoa-leave@lists.sentoa.org

Sentoa mailing list -- sentoa@lists.sentoa.org
To unsubscribe send an email to sentoa-leave@lists.sentoa.org

Hey Kelly! Wow, that’s a ton of great info, thanks for adding that for the archives! A couple of minor additions for posterity: Our cutlass bearings (the generic noun) are also Cutless bearings (the specific brand name, incorrect spelling intentional and a trademark). Duramax is also sometimes seen as Johnson or Johnson Duramax—same thing, especially if called “Cutless” as per above. Lastly, I’m curious/pondering the 4gpm of recommended flow to the cutlass bearings, and 10psi for the PSS. Since the PSS can be used on a slow boat with no pressurized water feed—just with a snorkel from the pss barb—in theory, the water floods into the log/stern tube from the back when you burp the seal at launch (or automatically if you have the snorkel setup with no pressurized raw water source). In that case, it seems intuitively like the cooling/lubricating water would never be exchanged, since there would never be enough velocity to create a venturi (I think that’s the correct word) and suck water out. Perhaps this is another reason nordic tugs opted for the pressurized source? But it does make me wonder about boats with no pressure feed. In the case of a sailboat, for example, the cutlass bearing could be fed with water from the front as it was underway; not the case on our boats. Any thoughts on that? It’s neither here nor there, just a curiosity point for me at the moment. Cheers for the great post! b > On Feb 7, 2025, at 12:02, Kelly Britz via Sentoa <sentoa@lists.sentoa.org> wrote: > > To add to this great post: I managed to track down specific maximum cutlass bearing wear along with other useful details on keeping the bearings healthy. > Duramax is the manufacturer of the cutlass bearing NT installs on at least the 37, 39, & 40's and also NT’s recommended source for replacement bearings. Duramax’s Tom Farkas (West Coast Sales, Marine) sent me detailed Duramax and US Navy materials on cutlass bearing lubrication/operation theory and various shaft clearance parameters. > Here are my take-aways from this material specific to a 2” NT37/39/40 propeller shaft: > New shaft-bearing clearance: Duramax P/N 870512100/”CALL” is the 2”IDx8”long nitrile rubber lined naval brass cutlass bearing for a 2” shaft, has an original manufactured ID of 2.006”-2.012” out of the box. > Running clearance: US Navy/NSTM “Minimum Operating clearance of bearings” (I assume after break-in) 0.017” clearance for a 2” shaft. > Max wear clearance: US Navy/NSTM “Total Clearance at which bearing should be renewed” for a 2” shaft is 0.091” (at ~3/32", that would certainly be visible and quite likely ‘thunk’ when lifting the prop and shaft!). > Wear factors: “Duramax Factors That Affect Cutlass Bearing Wear” > Load > Rubbing velocity > Time at 0 velocity > (suggests if vessel idle > 1 week, shaft should be rotated 450 degrees weekly) > Uniformity of loading > (I assume this includes all shaft alignment issues) > Velocity time interaction > Shaft and bearing roughness > Shaft and bearing combination > Water quality and contamination > Raw Water Temperature > Raw water lubrication temperature should be as close to ambient sea water temp as possible > Raw water feed connection should occur before heat exchanger > Raw water flow requirements: Duramax recommended raw water flow to the cutlass bearing should be 4 gpm for a 2” shaft, more is better. > Raw water pressure requirements: PYI Inc, says 10 psi of raw water pressure for their PSS Dripless Shaft Seal. > Additional material that Tom Farkas provided included a technical paper titled “Water Lubricated Rubber Bearings, the Principles of Design and Operation” by Michael Brakey. > Included in this paper was the following quote that likely addresses some of Steve Day/SINBAD’s silty raw water lubrication concerns: > “When a grain of sand is trapped between the shaft and the rubber, it is depressed into the softer material and rolled into an adjacent water groove where it is immediately flushed out of the bearing. With proper loading, rotational speed and clearance, the shaft will ride on a thin film or wedge of water. When the shaft actually lifts itself off the rubber lands and rides a water wedge, we have what is known as hydrodynamic lubrication. At this juncture both friction and wear decrease significantly.” > This M.Brakey paper goes on with several pages of detailed theory and calculations about bearing loading, shaft velocity, and thermal expansion in the determination of proper bearing-shaft clearances for water lubricated rubber bearings. > When I get a chance, I will combine all this detailed original material from Tom Farkas / Duramax / PYI that I’ve merely summarized here, then post it together to SENTOA/Maintenance so that it will be easier for others to find down the road. > It’s great to finally know more about our cutlass bearing parameters. SANDPIPER is now at 12,800 engine hours on the original cutlass bearings and we've been measuring 0.021-0.023” of shaft play and wondering where we stand. > Thank you Ben McCafferty, I will be adding a little in-line flow indicator on the raw water shaft seal/cutlass line and will attempt to measure pressure/flow rate before we go into the yard in April. > Good luck to Steve Day, I hope you get good news in the yard this week there in the UK! Please report back. > Regards, Kelly Britz > Sandpiper, NT37-042, 2001 > Edmonds/Seattle WA > > > From: Steve Day via Sentoa <sentoa@lists.sentoa.org> > Sent: Sunday, February 2, 2025 7:53 AM > To: South East Nordic Tugs Owners' Association (SENTOA) <sentoa@lists.sentoa.org> > Cc: Steve Day <s.day2905@gmail.com> > Subject: [Sentoa] Re: Cutlass Bearings & shaft seals > > Many thanks for all the replies, appreciated. > > I have measured the overall length of the PSS and it is exactly as it should be with 1'' of compression, I will compress a bit further and see whether this improves the black misting (new set screws). I have noticed that on tickover (600/900 rpm) there is a very slight 'wobble' felt on the stainless steel collar, this is less than 1mm of movement, but I can't feel any noticeable movement on the actual shaft. I'll get the alignment checked. > > Due to be lifted out in the next week or so, and the decision to change cutlass bearings and switch to lip seal or upgrade the PSS will then be made. > > Steve > SINBAD > 37-192 > > On Sat, 1 Feb 2025 at 22:20, Fire Fighter via Sentoa <sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org>> wrote: > Good idea Harry. PSS also sells a part made for this purpose, but a clamp is less money. > Tom > > From: Harry Hungate via Sentoa <sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org>> > Sent: February 1, 2025 2:07 PM > To: sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org> <sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org>> > Cc: Harry Hungate <wcx7106@gmail.com <mailto:wcx7106@gmail.com>> > Subject: [Sentoa] Re: Cutlass Bearings & shaft seals > > One more comment on compressing the bellows on the PSS shaft seal: After compressing the bellows sufficiently to obtain dripless service, install a hose clamp around the shaft up tight against the stainless steel rotor. This will keep the rotor from creeping--not everyone gets the allen screws (grub screws to the British subjects!) sufficiently tight. > Harry Hungate > >> On Feb 1, 2025, at 4:25 PM, Joe Pucciarelli via Sentoa <sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org>> wrote: >> >> >> >> I also had issues caused by a PSS seal not being properly compressed when it was replaced. I agree with Steve that following the specs in the PSS table should lead to a dry and clean bilge! However, it’s absolutely imperative to use new sets screws as stated in the PSS documents! >> >> Joe Pucciarelli >> MARJOE >> NT37-175 >> >>> On Feb 1, 2025, at 3:23 PM, sadler love via Sentoa <sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org>> wrote: >>> >>> CAUTION: External Email. >>> >>> >>> The last time I had my PSS shaft seal replaced, after a year or so, it began to spray/leak at medium to high rpm. >>> >>> On the PSS website, I found a table showing how much compression should be put on my seal, and discovered I needed to increase the compression a full inch. >>> >>> I did so, and all spray/leakage disappeared at all rpms. Apparently the seal was not properly compressed when it was replaced. So, you might want to go to the website and get the compression for your seal and check it. The table is here: https://www.shaftseal.com/marine/pss-type-a-seal.html >>> >>>> On Feb 1, 2025, at 12:23 PM, Steve Day via Sentoa <sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org>> wrote: >>>> >>>> Hi all, and greetings from the UK. >>>> >>>> My 2007 NT37 has now done 2300 hours, when I purchased the boat in 2018 it had done around 1100 hours. As far as I'm aware the cutlass bearings have never been replaced. The boat is in salt water which can be a bit silty on the UK east coast. No undue vibration when going forward, but a bit grumbly in reverse. >>>> >>>> Secondly, I have the PSS shaft seal, which I replaced like for like in 2019, whilst the seal does not leak per se, I do get the messy black mist spray that covers the area around the seal. >>>> >>>> So, 2 questions: >>>> - Have I gone beyond what would be a reasonable length of time / hours to change the bearings? (Does anybody have details of suitable replacements?) >>>> - Has anybody tried using lip shaft seals (thinking Lasdrop) instead of PSS and had totally leak free shaft and a nice clean bilge?. >>>> >>>> Thanks all >>>> >>>> Steve >>>> SINBAD >>>> NT37/192 >>>> >>>> _______________________________________________ >>>> Sentoa mailing list -- sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org> >>>> To unsubscribe send an email to sentoa-leave@lists.sentoa.org <mailto:sentoa-leave@lists.sentoa.org> >>> _______________________________________________ >>> Sentoa mailing list -- sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org> >>> To unsubscribe send an email to sentoa-leave@lists.sentoa.org <mailto:sentoa-leave@lists.sentoa.org> >> _______________________________________________ >> Sentoa mailing list -- sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org> >> To unsubscribe send an email to sentoa-leave@lists.sentoa.org <mailto:sentoa-leave@lists.sentoa.org> > _______________________________________________ > Sentoa mailing list -- sentoa@lists.sentoa.org <mailto:sentoa@lists.sentoa.org> > To unsubscribe send an email to sentoa-leave@lists.sentoa.org <mailto:sentoa-leave@lists.sentoa.org> > _______________________________________________ > Sentoa mailing list -- sentoa@lists.sentoa.org > To unsubscribe send an email to sentoa-leave@lists.sentoa.org