PSS Bellows Queation

[earlybird]

Apologies for another PSS thread!
Since my PSS seal is of unknown age, possibly 12+ years, I purchased a replacement bellows, which I fitted end of last week. My problem is that I can't achieve the specified compression of 20 mm for the 1" shaft size. Try as I might, 18mm was the maximum, and at that, I can't visualise being able to "burp" it on launch, the seal faces are pressed so hard together.
Since it was cold, I did try a warm soaked rag around it, without getting more than 18mm compression. Now back home, 150 miles from the boat, I've tried the old bellows, and find I can compress it 25 to 30mm without real difficulty. It seems much more flexible than the new item.
I'll contact Sillette, the suppliers, to-morrow, but meanwhile, has any-one come across this before?
(In another, current, thead, a poster mentions similar difficulty due to a displaced rubber bushing that was fitted to the bellows. I don't think that's the cause of my problem).

 

[doug748]

I think you are very good to be able to see the differnce between 20 and 18 mm in this context.

Going by my experience you will be ok. The key thing seems to be that it pushes up flat with a positive pressure.

I put a Jubilee clip (two in fact so they are balanced) on the shaft a couple of mm behind the rotor. This acts as a back up in case the rotor slips (it never has) more importantly it would let me see it there was any slippage. Tell the truth I never check it from one year to the next.

 

[rgarside]

When I installed mine a couple of seasons ago, due to the awkward position to get at it I couldn't push anything like hard enough to get close to the compression they specified - I ended up with a lever arrangement to compress it which enabled me to compress it with one hand while doing up the grub screws with the other. Its been just fine in service since then. I fitted it after getting very frustrated with Deep Sea Seals, which did not perform well.

 

[Old Troll]

PSS Bellows

Do you have the vent pipe system and if so is it neccessary to burp this type of seal on launch? The vent pipe allows the air to escape and water to come in. Also if in doubt of water coming into the bellows you can always loosen of the jubilee clip on the vent hose pipe nipple.

 

[Chalker]

With the vent pipe system you do not need to burp it to let the air out and water in..
If the shaft has been stationary for a while the seal could stick a bit which puts a twisting load on the bellows. Recommend to twist by hand and if necessary pull the faces apart.
Which is of course the same as burping it! But only necessary if its been stationary for a while.

 

[earlybird]

Thanks for responses. No, my seal doesn't have the vent pipe, I think that was a later feature, but "burping" the seal isn't my prime concern.
The bellows is meant to absorb some fore and aft movement of the shaft due to prop thrust and still maintain face contact. I've got good access to push the rotor hard along the shaft, but I seem to be compressing the bellows to the limit of its construction without getting the specified compression. Any further seems to be pushing on solid rubber. This seems to be putting undue pressure on the carbon seal, which will get even greater when the engine is put astern and the shaft moves aft by a small amount.
The Youtube installation video shows the bellows compression of 25mm on a 1.25" being applied by the fingers of one hand, and the installer isn't a gorilla! And I only want 20mm.
My old bellows was like that and allowed shaft movement either way if set to 20mm compression, so I'm puzzled.
I may be worrying unnecessarily, but this is a critical component and I'd like to meet the manufacturer's spec. bearing in mind the penalty for getting it wrong is at least the cost of another lift out and could be much worse!

 

[maej]

When I installed my PSS I also needed a lot of force to obtain the required compression. I had to use both hands hard to pull it and was just barely able to hold it steady with one hand while tightening the grub screws, mind you my position wasn't ideal for applying force. There is still scope there for further compression given enough effort though.

One thing to check is that the stern tube isn't protruding in to the bellows fouling the troughs of the ridges as that could prevent one of them from compressing and will start to cut in to the rubber if left that way. I had to position the bellows carefully to avoid this as the tube was longer than the cuff of the bellows.

As for burping, I find it isn't that hard despite the force because you only need to move one side of it to break the seal which requries a lot less force than pushing the whole thing back.

 

[earlybird]

An update on my seal. The suppliers tell me that the spec. of the bellows was changed 3 or 4 years ago to a tougher and harder material, although, of course, they hasten to add that there was no problem with the original ones.
That goes some way to explain the difference I'm seeing.
The recommended compression still remains at 19-20mm though. I'll go to the boat next weekend and give it another go. Perhaps I was worrying too much last time.

 

[Squeaky]

Good evening:

May I suggest that you be careful about increasing the pressure of the rotor against the carbon piece and bellows as this would increase the resistance between the rotor and carbon piece which might well cause the bellows to rip due to the twisting pressure.

Please don't think that the bellows is indestructible. See http://www.ybw.com/forums/showthread.php?289854-PSS-Shaft-Seal-problems/page2 and post 52 see how the bellows can tear although I don't think this is what caused my problem.

Cheers

Squeaky

 

[kacecar]

I've recently fitted a PSS seal on my own boat and, yes, I did come across the Earlybird's problem. I think one just has to persevere until the right compression is achieved.

On mine, compressing the bellows to the specified length was hard work. After numerous trials, errors and failures (accompanied by not a little bad language), success eventually involved a series of wooden spacers and a long lever - not quite brute force but disconcertingly close. However, the seal seems to work well, so all that effort proved worthwhile in the end.

 

[Squeaky]

Good morning:

I don't recall having any difficulty compressing the bellows to the specified length with the two units I had but then again I have good access to my shaft.

I am still floundering around trying to understand what went wrong with my two units which failed as I haven't been able to get a satisfactory response from PYI or Seaview (manafacturer and European dealer).

Lately I have been began to wonder if the production was not recently "outsourced" to some far eastern country resulting in the production of seals which are different than the original. For example the trouble compressing the bellows could be caused by the walls of the bellows being thicker than the original making it difficult to compress to the length originally specified.

Just a thought!!

Cheers

Squeaky

 

[bert49uk]

may be worth contacting ASAP as most of us have bought from them, it would be a good PR exercice and they may sell more units as a result