PSS SHAFT SEAL

[Richard_H]

Festive greetings everyone

Have recently inherited a Moody 35 with a PSS shaft seal installed.
The previous owner demonstrated this wonderful device to me suggesting every passage I make no matter how long or small I should briefly "squelch" the bellows allowing a small amount of water to filter into the bilge?? Previously I have only been used to stuffing boxes with loads of white grease!!
Question is - is squeezing the bellows the correct procedure to undertake on this device and since my boat dries out of the water daily on a drying mooring is their any other routine maintenance I should be undertaking? Does it need checking pre and post every passage?

The literature I have read implies you leave them completely alone throughout the sailing year - who is right?

Many thanks in antic.

Richard H

 

[steve6367]

The seal needs water inside to keep it cool. So each time you dry out there is a possibility that an airlock will form and stop the water cooling. That is why the instructions advise you to squash and allow a small amount of water to flow after you dry out. This is not normally a problem, but if you are on a drying mooring could be a pain. Having said all that, I have forgotten to do this a couple of times whilst away in the channel islands and it seems to be ok.

 

[Anthony]

I have one of these on my yacht, as I understand it (and as has worked for me in the 2 years I have had it), is that when you put the boat in the water you briefly pull the seal back (compress back the bellows) so as to pull the graphite type ring thing away from the stainless steel ring on the shaft, thus allowing the air out and the beloows to fill with water.

This is because they are water lubricated, and need water to work. I dont regularly do it whilst in the water, and on the odd occasion I have played with it while poking around the engine I have found it to still be full of water, and no noticable signs of wear as yet.

They are often at the boat shows is you are going to the London b.s. u could have a chat with them to ease your mind.

Anthony

 

[Richard_H]

Steve
Thanks for posting. Your reply seems sensible enough and good enough reason to monitor it on a routine basis. Time will tell if it needs to be on every occasion - better safe than sorry. Many thanks
Richard H

 

[tugboat]

Are you sure yours is a PSS as that type is supposed to incorporate an oil reservoir and thus doesn't need any attention. Other makes such as the Manecraft Deep Sea Seal uses water to lubricate and therefore it is essential to ensure that the sterntube is filled with water right up to the seal. This is done by 'burping' as you describe. As your boat dries out and the sterntube can drain out it would be necessary to 'burp' before each trip. If you have a lot of mud in suspension in the water this could lead to premature wear. I think it is recommended to renew about every 5 years.

 

[ex-Gladys]

PSS does not have oil reservoir, it consists of stainless disc attached to propshaft with a carbon composite part atttached to the stern tube via bellows. The slow speed (<1200 RPM IIRC) requires only allowing water in on launching. The high speed version has a water feed to the carbon bit to improve cooling.

Full explanation is here PSS Shaft seal

Amber has had a PSS for 10 years. Just about to replace with the same as the bellows need replacing every 5-7 years.

 

[Robin]

The PSS is NOT oil filled but water cooled and is a much better seal than the Deep Sea Seal. I changed our DSS for a PSS last year. Ours is the so-called high speed version with a water feed to it, but in our case the feed is not fed pumped water but is simply used to take a tube above the waterline as a permanent bleed for any air ingress, even though we never dry out. This was a suggestion fron PSS who are very helpful, from their factory in the USA. See:-

http://www.shaftseal.com/

 

[steve6367]

Sounds like a great idea. Does the pipe completly solve the problem of airlock when you dry out? Might be the way to go on my boat when it need replacing.

 

[Robin]

No airlocks at all, even when we launched first time after fitting it as you could see the water level in the clear hose we used. It also removes any possibility of a venturi effect sucking the water out of the stern tube and the seal running hot which I believe is what has happened to Charles-Reed who posted about it last year. It keeps a small head of water in the tube to keep the seal water filled.

 

[tugboat]

Sorry if I caused any confusion. Not knowing the PSS seal personally I looked up an article to check - Doh! There seem to be 2 that go under the PSS title, one from Halyard Marine that I saw & latched onto, and another that I didn't notice which, from the other posters' comments, is the one in question. That'll teach me to be more careful /forums/images/graemlins/crazy.gif

 

[Robin]

The Halyard Marine oil filled seal is no longer available, it was good but very expensive which meant not many were sold I believe. There is a similar one to the PSS made in France which looks as if it would be OK too. One of the problems with the PSS was clamping the shaft half of the seal exactly at 90 degs to the shaft. The PSS is different and has a solid S/S rotor which clamps easily on the shaft and seals to it via 2 stationary O-rings, it is altogether a more robust piece of kit IMO.

 

[Sam_Salter]

I've had a PSS shaft seal on my C&C 26 for about 4 years. I burp it when I launch in May & that's it till I pull her out in October! I don't dry out however, I keep her on a mooring all summer. But as a previous reply said, I forgot to burp it once, & used it all summer with no ill effect.
These seals are very popular in Canada & the States. I'm a member of a few forums over here & don't read any complaints about this seal.
sam
C&C 26 Skye II
Ghost Lake Alberta.