PSS type shaft seal

[Tim Good]

That's not what the fitting instructions say. Why is it that we seem to have a spate of people who ignore manufacturers' instructions?

Agreed. I've never seen instructions for PSS type seals which say "more compression the better". This is what they told me:

"
Good Morning Tim
Thanks for your email. the compression on these seals for the 1.5" shaft should be 10mm.
To check this remove the stator ring, compress the bellows and let it relax. mark the position and refit the stator ring to finish 10mm up the shaft.
To much compression will result in excessive wear of the carbon and insufficient will allow leakage.

Kind Regards

Tom Clarke (BSc Hons) Senior Sales Engineer tomclarke@mmp-i.com Michigan Marine Propulsion

 

[NDG]

Just to provide an update on this. I went to the boat this morning and measured the length of the unit to understand the compression by comparing with the table in the manufacturers instructions. It was a bit difficult to measure because unless you are a 5 year old child with unnaturally long arms it’s hard to get to the seal with both hands, but it looked like the length was c140mm whereas the recommendation would be 170mm with 10mm compression +/- 4mm, i.e. 156-164mm.

I backed it off by just over 10mm and ran the engine for about 20 mins in gear with a few revs on. Initially some dust was ejected but after a few minutes it seemed to settle down and nothing emerged for the final 15 mins or so, which is much better.

It seems almost certain that it had too much compression. I’ll keep an eye on it and there is still some room to back it off by a further 5mm or so if I need to, but I’ll take it in stages and see what happens after the next proper motor.

This seems like good progress. Thanks to everyone for the assistance, It’s been really helpful, especially pvb for identifying the seal and pointing me toward the maker‘s website.

 

[pvb]

Just to provide an update on this. I went to the boat this morning and measured the length of the unit to understand the compression by comparing with the table in the manufacturers instructions. It was a bit difficult to measure because unless you are a 5 year old child with unnaturally long arms it’s hard to get to the seal with both hands, but it looked like the length was c140mm whereas the recommendation would be 170mm with 10mm compression +/- 4mm, i.e. 156-164mm.

I backed it off by just over 10mm and ran the engine for about 20 mins in gear with a few revs on. Initially some dust was ejected but after a few minutes it seemed to settle down and nothing emerged for the final 15 mins or so, which is much better.

It seems almost certain that it had too much compression. I’ll keep an eye on it and there is still some room to back it off by a further 5mm or so if I need to, but I’ll take it in stages and see what happens after the next proper motor.

This seems like good progress. Thanks to everyone for the assistance, It’s been really helpful, especially pvb for identifying the seal and pointing me toward the maker‘s website.

Happy to help! Did you make sure that water was reaching the carbon/steel interface?

 

[NDG]

Happy to help! Did you make sure that water was reaching the carbon/steel interface?

Yes, i burped it and ensured a good flush of water over the two facing parts. Fingers crossed.

 

[Tim Good]

Yes, i burped it and ensured a good flush of water over the two facing parts. Fingers crossed.

I’ll just add, Vyv Cox reminded me of an important thing to consider when laying up ashore for a while. Since salt water can be trapped With any air between the stainless ring and carbon, then crevice corrosion could form. He saw this happen personally I believe.

So the moral is to back off the ring and rinse with fresh water. Perhaps leave it backed off until you splash again. I’m only saying this as I recently laid up for 18 months So I felt it was a worthwhile precaution.

 

[greeny]

Good point northcave about leaving it backed off.. The last one I played with had been on the hard for 9 months and when separated the stainless ring face had definite creviss corrosion on it. So much so, that I got it refinished and then lapped it down on a flat plate with glass, with first grinding paste down through the grades and then a fine cutting compound to finish it off to the best surface finish I could get. It's worked fine for the last 8 months with no sign of wear or leakage so seems to be ok now. Next time the boat is out for a while I will release the ring and move it away from the carbon seal and rinse with fresh water as part of the laying up procedure.

 

[NDG]

Thanks, that sounds like good advice. Will remember that.

 

[Hoist]

That's not what the fitting instructions say. Why is it that we seem to have a spate of people who ignore manufacturers' instructions?

I was just quoting my experience having had one before.

apologies if I offended

 

[vyv_cox]

Good point northcave about leaving it backed off.. The last one I played with had been on the hard for 9 months and when separated the stainless ring face had definite creviss corrosion on it. So much so, that I got it refinished and then lapped it down on a flat plate with glass, with first grinding paste down through the grades and then a fine cutting compound to finish it off to the best surface finish I could get. It's worked fine for the last 8 months with no sign of wear or leakage so seems to be ok now. Next time the boat is out for a while I will release the ring and move it away from the carbon seal and rinse with fresh water as part of the laying up procedure.

There is a photo of the damage to the stainless rotating face on my website. I reversed it to use the other side and bought a spare but not needed it since I began to fresh water flush.

 

[slawosz]

Hi,
I will be changing the cutlass bearing on Sadler 25 with the PSS seal. I am not sure if I can remove PSS (looks quite new), or really, the stainless collar, or should I do the procedure with the shaft in place and just remove the propeller?

 

[MoodySabre]

Hi,
I will be changing the cutlass bearing on Sadler 25 with the PSS seal. I am not sure if I can remove PSS (looks quite new), or really, the stainless collar, or should I do the procedure with the shaft in place and just remove the propeller?

I should start a separate thread for This to attract Sadler 25 owners. If you can do it without removing anything but the prop then you will save a lot of work.