PSS Seals

pcatterall

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The deathly silence will, hopefully, indicate no problems!!
I plan to fit one this winter as I seem to have an unusual problem with crevice corrosion on the shaft under my lip seal! Due possibly to standing unused for longish periods in Med water.
Hope is that if it occurs with a PSS seal then it will be the seal rather than the shaft that suffers..
 

vyv_cox

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The only fault I have had also happened to another user who contacted me. This was corrosion pitting of the stainless steel face, probably due to not flushing with fresh water before winter layup. I reversed the shaft seal and have not had a recurrence, although I do now carry a spare. Otherwise, in 8 or 9 years of fairly high useage, maybe 1500 hours, absolutely no problems and no maintenance activities other than ensuring the faces are wet before first start each spring.
 

rogerthebodger

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I also have a PSS seal with no problems over the last 6 years. I have found that the carbon can "stick" to the rotor after a months layup. I simply unstick it by hand each time I visit my boat
 

Tim Good

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Hi Mike,

There is a massive thread here which is interesting but I'm unsure if it is a truly accurate representation as the OP seems to go off on one a bit: http://www.ybw.com/forums/showthread.php?289854-PSS-Shaft-Seal-problems

My own experience is limited but I am having issues at the moment. I posted here: http://www.ybw.com/forums/showthread.php?436522-Prop-Shaft-Knocking-in-high-revs

Basically the system is great and witha new expensive shaft I thought the PSS would be great. However, although my shaft is new and aligned and I have an aqaudrive keeping vibration down to a minimum, the carbon face wobbles. This is then exacerbated in high revs where it wobbles sufficiently to knock on the shaft. Now this might be down to a one off mis-alignment in the faces of the carbon and stainless ring, but it is my first experience of the PSS. Other than that, it seems excellent so I don't think my experience is anything to judge it by per se.

Even if Michigan Propulsion (makers of my PSS) come back and say they'll give me a knew one, then it is going to be a lift out job.... unless I am brave enough to remove / swap in the water.
 

ex-Gladys

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I had one on previous boat, where the fitting space was a bit wrong as I recall, and the minute you even touched it water p**sed in. Changed it the first winter for a Volvo, but currently (different boat) have a lovely old fashioned stuffing box which I love. If I'd had a PSS (or probably even a Volvo) I believe Gladys would have sunk, as I've had some engine mount and shaft problems over the years...
 

<152587>

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My honest advice to anyone considering a seal that relies on the compression of a piece of rubber to seal the ocean from the bilge is to see a shrink! Have professionally been involved with 3 incidents of this sort of seal nearly causing loss of vessel. Go for the conventional stuffing box, used for over a century and pretty well infallible.
 

vyv_cox

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My honest advice to anyone considering a seal that relies on the compression of a piece of rubber to seal the ocean from the bilge is to see a shrink! Have professionally been involved with 3 incidents of this sort of seal nearly causing loss of vessel. Go for the conventional stuffing box, used for over a century and pretty well infallible.

In the course of several threads on the subject I managed to find a list of the yachts and motorboats that fit PSS seals as original equipment. It ran to several closely-typed pages and included builders all over the world. These seals have been produced in the hundreds of thousands, in the vast majority of cases functioning perfectly reliably. Of course, people will always find a way to f**k things up, hence the small number of bad experiences.

Not to mention Volvo seals, which are 100% rubber and equally reliable.

So far as compressed rubber sealing a few inches of water is concerned, I worked extensively with elastomeric seals on 400 bar gas pressure systems that had good reliability. If the design is rght and operators know how to use it, the equipment will be fine.
 

superheat6k

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My honest advice to anyone considering a seal that relies on the compression of a piece of rubber to seal the ocean from the bilge is to see a shrink! Have professionally been involved with 3 incidents of this sort of seal nearly causing loss of vessel. Go for the conventional stuffing box, used for over a century and pretty well infallible.
Were any of the incidents referred to specifically involving a PSS seal ? If so had their instructions for installation and maintenance been followed ?

The two on my Turbo 36 appeared tired after around 15 - 20 years service, but not a droplet from them. I only changed them because I had to change the cutlass bearings. The instructions state a 7 year service life, which would be of interest to an insurance company if one failed after this time, but I doubt the likelihood of failure increase much for double that for lightly used pleasure boats.

If removing one note that each grub mount has two grubscrews, the first outer grubscrew has to be fully removed to release the inner.

More info available at their website www.pyiinc.com

Aquafax hold stock or can get them very quickly.
 

halb

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You ask if anyone had had any problems with this b***** heap of ****, my boat had one fitted prior to my ownership, this was done by a yard in Falmouth, no DIY involved.
Last August Bank holiday, it failed whilst boat was on a visitor's buoy in Falmouth, RNLI pump out etc, etc, insurer's surveyor called, he informed me that he see's several of this type of seal failures each year, long story cut short, the repair bill was approximately £20k.
I hope you weren't taken in by the stands at various Boat Shows saying "fit and forget" this is not so, they need regular checking. Did you fit it yourself? If so did you use locktite on the grub screws and did you torque them to the correct amount, if not, do so if you don't want the same thing happening to your boat.
I would suggest that you and all users of this type of seal, Google 'PSS Seal failures.
I now have an old fashioned Stuffing box, so it drips under motor, so what, not very many reports of sinking or near sinkings reported by users of this type of seal.
Good luck and sleep well at night, I do now!
Jon
 

Dougal

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THIS is how GOOD they are, or at least can be... I have one fitted. Was on the boat when we bought it, and we've had the boat over 8 years. My guess would be that its at least 10 years old.

On this boat, is a Perkins 4108, fitted rather badly. I'd be EXTREMELY surprised if alignment is accurate. Then there's an old Hurth 2:1 gearbox, fitted directly to a 25mm shaft. The shaft has almost FIVE feet unsupported before the PSS seal and tube. That shaft has a 'run out'. By that, I mean it's bent!!! Of the three 10mm retaining bolts (grub screws on some), I now discover one is sheared off!!!! As I'm sure all would agree.... a recipe for disaster?

The PSS seal has NEVER allowed a single drop of water in, that I didn't deliberately plan. Make your own conclusions....
 

john_q

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We bought a project boat, a S & S 31 long keel with a YANMAR 3GM30 and PPS seal on it. The seal is probably quite old as it has no water injection point

When we got round to hauling the boat, we found some of the fibreglass on the outside of the boat surrounding the propeller tube before the cutlass bearing was missing. When we looked a bit closer, we also found that the cutlass bearing was worn out, the engine was way out of alignment and the mounts were gone

So we had the tube area reglassed, replaced the cutlass bearing, replaced the engine mounts and re aligned the engine. (The re alignment was a real pig as the whole set up was so far out and we had to modify the mounts)

The next outing with my sister in charge they motored off at 2,500 RPM and noticed after a while that the floor boards were floating, so they reduced revs and checked out the boat – no leaks. We eventually found out that more than 2,200 RPM in gear the seal leaked. This was solved by re setting up the seal/bellows compression/clearances

So the moral of the story is

If you have a PPS seal and re align your engine, check the seal is still set up correctly

Note this is not in the instructions I have.
 

Caer Urfa

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The only fault I have had also happened to another user who contacted me. This was corrosion pitting of the stainless steel face, probably due to not flushing with fresh water before winter layup. I reversed the shaft seal and have not had a recurrence, although I do now carry a spare. Otherwise, in 8 or 9 years of fairly high useage, maybe 1500 hours, absolutely no problems and no maintenance activities other than ensuring the faces are wet before first start each spring.

Hmmm a mixed response!

Hi Viv, what do you mean exactly of quote 'no maintenance activities other than ensuring the faces are wet before first start each spring' unquote, how do you ensure the faces are wet! (I sail all year round)

Following me fitting a new cutlass bearing and new shaft the seal was fitted professionaly last week by a local boatyard after re aligning the shaft to the engine/gearbox.

From comments I obviously need to monitor it carefully but hope its all it is cracked up to be otherwise its back to a new conventional stuffing box.

Thanks to all for your replies so far

Mike
 

Caer Urfa

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2 years so far and zero problems.

I carry a roll of Denso tape on board just in case of any problems with shaft seals or sea cocks. Hopefully I'll never use it.

Hi Wully

Pleased someones happy with their PSS:)

Do you do any maintenance on it other than making sure all the locking grub screws are tight, my engineer also fitted a jubilee clip after the PSS seal as a locking back up.

Mike
 

superheat6k

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The PSS I have recently fitted came with the thread locker already applied, but the jubillee clip on the shaft in front of the rotor is belt and braces.

i would pay money to watch someone apply a torque wrench to the PSS grub screws on a Turbo 36 - those were done up in a blind recess 1 flat at a time almost at arms length. Note the Allen key is imperial not metric, but the correct size is supplied with the seal.
 

Topcat47

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I fitted one a couple of years ago. This year I did some work on the boat ashore and tried to reset the clearance. I could not fully compress the bellows which appear not to have returned to their original length when I removed the collar. I've not got a leak and monitor things pretty carefully, but I"m not completely happy with the situation.
 

vyv_cox

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Hmmm a mixed response!

Hi Vyv, what do you mean exactly of quote 'no maintenance activities other than ensuring the faces are wet before first start each spring' unquote, how do you ensure the faces are wet! (I sail all year round)

RTFM! :). The instructions advise that if the boat has been out of the water for a time (a month?) the seal faces should be wetted before the engine is started. If access is simple this only means pushing the bellows back after launching to let a little water in. For me it is difficult as there is a lot of kit on top of the shaft tunnel, so I pour a jug of water over mine the day before launch. The graphite face will tear if run dry. This is standard practice for all mechanical seals, of which there are over 1000 in every refinery. In your case if the boat is always afloat it doesn't apply.
 
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