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Old 16-05-2018, 08:19   #1
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PSS dripless is dripping, but what are these grooves?

My lightly used PSS is dripping after 3 seasons. At first, we thought we would just slide the collar aft to add more compression for a tighter seal. But, when we moved the collar, we found these machined grooves on the shaft, under the collar. See the pics.

Why are they here? I'm replacing the complete PSS seal and fear that when I slide the new collar over these grooves, the O-rings will get damaged. Maybe this is why it was leaking in the first place...

Very close inspections of these grooves seem to indicate that they were intentionally machined into the shaft. Buy why?

Thoughts? explanations?

Thanks!!!!
Rob







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Old 16-05-2018, 11:17   #2
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Re: PSS dripless is dripping, but what are these grooves?

I can't imagine why someone would create a stress riser that serves no purpose but I didn't make the shaft. And I also profess ignorance to how the seal rides on the shaft but could it be the lip seal creating that groove? I thought PSS (which I have BTW) used a flat seal that essentially lapped into another face to create seal?

Anyways I'm sure another will be along to explain that.

But what I can tell you from much motorcycling and rebuilding hydraulic forks is the trick we used to prevent nicking the new seals. Just use a plastic zip lock bag and cut so you have 1 ply. Wrap around shaft and lube with something. Slide seal up and then remove plastic.

I'd probably polish that shaft with very fine grit paper to remove any burrs and rust that I can see before doing that.
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Old 16-05-2018, 11:40   #3
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Re: PSS dripless is dripping, but what are these grooves?

Great Tip about the plastic baggie!!!! I've heard of that before but wasn't thinking about it at all!!!

The collar clamps to the shaft with set screws and spins with the shaft. There are O-rings that seal between the shaft and collar. The O rings are inside the bore of the collar.

There is a rubber bellow with a graphite ring that clamps to the cutlass bearing housing aft of the collar. The graphite ring and collar rub together to seal out sea water. You can loosen the collar and slide it fore or aft on the shaft to set the amount of compression in the rubber bellow which controls how much pressure the stationary graphite ring presses against the spinning collar.

Super simple!! They are supposed to be maintenance free for a million-billion hours!!

Mine is a 3 yr old boat and I think it was damaged during the factory install.
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Old 16-05-2018, 12:04   #4
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Re: PSS dripless is dripping, but what are these grooves?

Interesting. I need to check mine. I have a V Drive so the transmission sits directly over the shaft seal and access is very poor. I have a molded in catch pan that seal is in so I would know immediately if it was leaking. Mine has been perfect for as long as I have owned it but knowing the previous owner he didn't do anything. Have to think it's probably going on 10+ years.

I should have checked when I had skeg and rudder off last summer while having insurance repairs done but it wasn't in the scope.

I think I'd need to pull the transmission to get access.
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Old 16-05-2018, 12:38   #5
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Re: PSS dripless is dripping, but what are these grooves?

I suspect the stainless steel collar has been rotating on the shaft. The grooves have been caused by the two “O” rings spinning on the shaft probably with some underlying crevice corrosion.

The stainless steel collar should be locked to the shaft with allen bolts, but they can slip if not tightened correctly.
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Old 16-05-2018, 13:18   #6
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Re: PSS dripless is dripping, but what are these grooves?

I dont have that seal but seem to remember reading that they can only be tightened once, if you need to loosen them, they have to be replaced, or they will slip?
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Old 16-05-2018, 13:27   #7
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Re: PSS dripless is dripping, but what are these grooves?

Quote:
Originally Posted by noelex 77 View Post
I suspect the stainless steel collar has been rotating on the shaft. The grooves have been caused by the two O rings spinning on the shaft probably with some underlying crevice corrosion.

The stainless steel collar should be locked to the shaft with allen bolts, but they can slip if not tightened correctly.

That makes sense and what we thought might have happened. Looking closer, we see the divot in the shaft caused by the set screw biting in during the install. It has never moved since it was originally tighten. The set screws are supposed to dig into the shaft a little bit. Which it did you can see the set screw marks in the pics. If the collar spun, we would expect to see a large groove caused by the set screw.
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Old 16-05-2018, 23:48   #8
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Re: PSS dripless is dripping, but what are these grooves?

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Originally Posted by IL1333 View Post
If the collar spun, we would expect to see a large groove caused by the set screw.
Unless the set screw loosened so much it was not touching the shaft at all.

The set screws can easily become loose. PSS have detailed steps to stop this happening such as not reusing the screws. They can only be tightened once and then should be replaced. PSS also stress the importance of adding two screws to each hole so one screw acts as a lock nut.

The other thing to check is the size of the seal. The stainless steel collar needs to fit very precisely over the shaft. If the collar is even slightly too large it would cause these problems.

If someone has skimmed the shaft at some stage to remove corrosion, this can be enough to cause the collar to be too loose. From memory the stainless collar has the size permanently embossed on the side. Check the website to determine what sized shafts are acceptable for your collar and then measure the shaft diameter with some callipers at the point where the seal is fitted rather than the propellor end.

If the collar has not been spinning the only other possibility is crevice corrosion under the “O” rings. Do you know what type of stainless was used for the shaft?
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Old 17-05-2018, 00:33   #9
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Re: PSS dripless is dripping, but what are these grooves?

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Originally Posted by IL1333 View Post
..............

Very close inspections of these grooves seem to indicate that they were intentionally machined into the shaft. Buy why?

Thoughts? explanations?

Thanks!!!!
Rob







It certainly looks intentional! Perhaps they machined into the shaft mistakenly for the o ring of the collar to sit in. Does the groove line up with the o ring and the mark of the set screw?

Can you refit the collar slightly along the shaft so the new o ring will miss this groove?
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Old 17-05-2018, 10:45   #10
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Re: PSS dripless is dripping, but what are these grooves?

I have the same setup. The picture looks like a dirt line to me. Is there a groove that you can feel after cleaning it up with some 1500 grit wet or dry sandpaper? The O rings should make up for slight differences in diameters. Grease the shaft with teflon grease when moving the collar - it should offer a bit of resistance. Double set screws is essential, it is spinning at a good rate.

Check the faces for wear. The collar should be smooth and shiny where it contacts to carbon sleeve. The carbon should also be smooth and shiny. If not the bellows may not have been compressed enough. If not they should be cleaned up on a lathe. The stainless should be polished.

Mine is also on a V drive transmission and yes, it needs to be removed for access.
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Old 17-05-2018, 19:08   #11
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Re: PSS dripless is dripping, but what are these grooves?

Had an identical issue in SE Asia with deep clearly defined groove on the shaft. I thought it may have been a loose collar that eroded the shaft, ie the grub screws weren't tightened enough.When I queried the mechanic he claimed that it was caused by stale seawater trapped between the seals.
I am not convinced, but luckily the shaft is way over size. Peter
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Old 17-05-2018, 19:14   #12
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Re: PSS dripless is dripping, but what are these grooves?

Ok, I have installed many of these PYI PSS seals, as a professional marine mechanic. In my not so humble opinion the groove was caused by a previously installed lip seal or such. There are 2 existing installation problems, the graphite ring mounted in the bellows is not concentric with the shaft, the water feed hose is pushing the graphite ring off center by not having a fair lead and being too stiff. I would guess there is a lot of vibration causing massive leakage as per the excessive staining and deposits.
I currently have 2 boats of my own with pyi seals (3)and show no signs of such problems. By the way I would not ever install any other seal even when the owner brought one to me. Never had one not agree with me after I pointed out the differences. In my retirement, I am over seeing a new pyi seal installation to rectify a situation where the packing gland was completely unreachable.
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Old 20-05-2018, 20:49   #13
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Re: PSS dripless is dripping, but what are these grooves?

just finished replacing the bellows on a PSS with a 1-1/8" shaft, ( after 12 years in use, carbon and face still perfect although bellows replacement at 6 years is recommended) the compression specified for the that shaft size was 3/4" , and from the photos its seems that there was much less than that in this case and that may be the source of the leak, as mentioned earlier new set screws should be used and backed up with another set screw with locktight blue, the correct amount of compression may correct the leak and the O rings will not be on the same damaged location which should as mention earlier be cleaned up with fine emery)
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Old 21-05-2018, 06:01   #14
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Re: PSS dripless is dripping, but what are these grooves?

I suggest sendinding your pix to PYI with your questions, they are always helpful. This is an example of why it’s hard to warrantee boat parts , you don’t know what someone has done in the past.
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Old 21-05-2018, 07:37   #15
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Re: PSS dripless is dripping, but what are these grooves?

Is it possible that the groove was there before you installed the PSS shaftseal? If flax or similar packing was used before the PSS the groove may have been caused by a bit of grit stuck in the packing. I don't think it was caused by the o-ring slipping. If memory serves, the 0-ring is on the outboard side of the set screw, not the inboard. In fact, it looks like you can see it's mark in the photos.

I have found that, with time, the bellows on the PSS shaft seal loose a bit of their "oomph". I have squashed mine down more than the recommended 3/4" since installation 7 years ago to address small leaks. You might give that a try. If you are worried about damaging your o-rings you could fill the groove with Marine Tex or similar and sand it smooth before sliding the collar back.
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