Dripless Shaft Seal leaks

Roland5048 · Sep 30, 2017

Most likely a PSS seal. Google dripless seals. I had one replaced in Jan. It has a vent tube. They should last 7 - 10 years. I don't think they can be replaced while in the water. I do know you would get one heck of a lot of water coming in. After these many years, it might just be wise to pull the boat and replace. That would also be a good time to do other bottom work. If it fails, it could sink the boat. Keep us up to date.

Ted · Sep 30, 2017

It's a PSS dripless shaft seal. You can find information about the PSS Shaft Seal here:
http://www.pyiinc.com/downloads.html
Burp the seal by compressing the bellows to allow trapped air to escape from the bellows. Water will flush the area between the two mating surfaces. Don't be afraid to allow a good flow of water to enter the boat. After you release the bellows the flow will stop and you should no longer have a problem. Sometimes small pieces of "whatever" get between those mating surfaces and can cause a slight leak. There should always be water inside the bellows. Burp the air out to allow water to occupy that area. This should always be done after the boat is put back in the water after a haul out. The PSS shaft seal is a great product and when properly maintained will help keep your bilge dusty dry.

Allan12210 · Sep 30, 2017

Its hard to tell on yours, but they are supposed to have two set screws stacked on top of each other (that's 4 total). The second set screw is to keep the first one against the prop shaft from coming loose. Mine is spec'd for a 3/4 inch amount of compression of the bellows before tightening to the shaft. Whenever the setscrews are loosened, it is required to replace them with brand new ones. Otherwise there is a risk they won't bite into the shaft and the stainless steel ring can slip. If you contact PYI they can probably tell you the length of the bellows in its uncompressed state, then you can figure out how much compression yours has. At least you would know if it is set up correctly. Maybe yours has slipped back a little, especially if the set screws were put back used and not backed up. This can all be done in the water if you don't push it back enough to take all the applied load off of it.

I've had mine since about 2000 and replaced the bellows in 2011 even though it still looks great. I really like it and the dry bilge. And mine does not have a vent either. As Ted says, burp it whenever the boat has been hauled or if you suspect some debris in between the stainless ring and the carbon fixed face. You just need to crack it back a tiny bit and you'll hear the hiss of air then water will flush out. Contamination between the faces is rare, but not impossible I suppose. I've never experienced that.

Allan12210 · Sep 30, 2017

I'll go out on a limb as well. If you look at the photo of mine, it looks like my bellows is compressed more than yours. They look like the same model on both yours and mine. From both my picture and your video, I compared the ratio of the ring thickness to the bellows pitch. Mine is 40% of the ring thickness while yours appears to be 92.5%, or less compression than mine. I just hauled last week and it was rather hard to push the bellows back to burp it. Yours seems to slide easily, i.e., less pressure than mine. So, maybe it slipped or was never installed right. That's easily corrected.

Good luck.

JamesG161 · Sep 30, 2017

I appears that the seal has been run in Dry mode or Air trapped in the bellows.

It is a PYI seal. The bellows has "Made by PYI" moulded in it.

Ted's post #3 has their web link.

I called them directly and they will help you.
______
It must be an older seal [newer seals have a vent]. Both you and Allan have no visible purge on the Carbon/Bellow side. Note current model: PYI says they can run a dry seal, not to longevity of running dry.

If you are seeing water while underway, you Carbon face is worn and/or your engine mounts could be softer than when the seal was installed.

The lateral movement of the Bellow is not a good thing.

Do you see a water leak in a slow reverse? Reverse will compress the bellows or tighten the seal face.

Jim...

Allan12210 · Sep 30, 2017

And finally (until the next time

) are the two hose clamps at the carbon face sufficiently tight. It looks like the salt crystals are between the rubber bellows and the backside of the carbon.

Rick D · Sep 30, 2017

Listen to Allen. I have had them on two boats spanning almost 30 years. There is not enough compression on the seal. You need to replace the set screws (note 4 of them). I wouldn't worry much about the salt build-up; probably from leakage. But clean it up. Originally, the bellows was recommended to replace in ten years; now six. I have done mine a few years before ten. However, the bellows does need to be adjusted some time before replacement. You simply remove (all four) set screws and slide the assembly to to tension it. Then replace the set screws using lock-tite and you are good to go. Schedule a bellows replacement next haul-out. PM me if you want more info.

SG · Sep 30, 2017

The SS "Donut" is supposed to compress against the carbon fiber piece which forms a seal with the bellows.

You should have i) double set screws (i.e., after the first set of set screws, you back another set of them on top of each of the ones) so they lock themselves in; and ii) you should have something that keeps the SS donut from sliding toward the engine -- that way, it can NOT release completely regardless.

For the second "ring" that keeps the donut in place, you can use a specially designed fitting from PSS, you can find them from McMasters or other supply houses (you want a SS one); or some people use a shaft zinc. The back-up to the donut does nothing but make sure the donut can't move forward. The only downside of the zing, or some hose-cut-in-half and clamped with hose rings, etc. is that IF you got your hand or some article of clothing caught in it, it could be a mess. If the fitting is protected, or you nothing every gets in the spinning shaft, then something cheap will work.

I would FIRST temporarily put some thing on the engine side of the donut that would keep it from moving much toward the engine. (You can cut a hose in half, use some hose clamps, or self-amalgamating tape.) Then I would carefully loosen the set screws enough to allow you to compress the bellows more. You can call PSS if you have a question. (My guess, your donut has creeped back a good 3/8" to 1/2" back.).
I would probably get some warm water and clean the carbon block a by douching it. You might even use a little white vinegar to dissolve the salt. Then douche it with water.

Then tighen things up. Start the engine and see if it seals.

IF you have left it this loose, the carbon block MIGHT have been damaged, but I think not.

njlarry · Oct 1, 2017

Rick, when replacing I assume you have to pull the entire shaft out. The shaft to trasmission coupling has to removed from the shaft. How hard was that and does a machine shop have to reface the shaft and new coupling?
Thank you.

JamesG161 · Oct 1, 2017

njlarry said:
reface the shaft

Not needed.

This is a rotating mechanical seal, not packing or lip seal which can grove a shaft.

The wearing surface is the carbon composite disc, which engine side end of the bellows [flexible mechanical spring].

The fixed Bellows are compressed at time of installation and flex as the engine moves in forward and reverse thrusts.

The rotary part is Stainless and is set screwed to the shaft.
__________
The black specs shown on the walls of the boat, are the Carbon composite being sprayed as it wears abnormally.
The lateral movement of the bellows is not normal. This strongly suggests he has lost the "spring effect" of the bellows.

Jim...

jviss · Oct 1, 2017

According to the manufacturer, these should be renewed on a six-year schedule. A kit is about $85. It includes a new bellows, clamps, set screws (which should not be re-used), etc.

You should look at their webiste, which has an excellent explanation of components, how it works, etc., with videos, manuals, price lists.
http://www.shaftseal.com/

Rick D · Oct 1, 2017

I'm not familiar enough with a Cat 30 to know if there is enough room to replace the bellows without pulling the shaft. However, the unit you have in there now can be adjusted to add compression to the bellows which will hopefully tide you over until the next haulout. No need to disconnect anything; just remove both set screws and replace them with new ones and some lock-tite after sliding the collar back against the bellows.

FastOlson · Oct 1, 2017

jviss said:
According to the manufacturer, these should be renewed on a six-year schedule. A kit is about $85. It includes a new bellows, clamps, set screws (which should not be re-used), etc.

You should look at their webiste, which has an excellent explanation of components, how it works, etc., with videos, manuals, price lists.
http://www.shaftseal.com/

Following the advice from PYI is fine and advisable, but be aware that their 'six year renewal ' is a change from a previous decade when they would say 10 or even 12 years. This revision was reportedly mandated by their lawyers and not their engineers. Same background decision-making went into their dropping the non-vented fitting that was intended and well-described for use on boats whose speed under power was always under 12 knots.
Potential liability risk is a strong motivator, whether deserved or not.
We have had this great product since 1995, and are on our second bellows, and it replaced the original that looked like new when it came out.
A dusty bilge is a Good Thing.

Meriachee · Oct 1, 2017

Part of the sealing methodology is having water against the mating surfaces. When the boat is in reverse, cavitation can force air up there and cause the surfaces to run dry. The carbon ring will wear when there's no water in there. It spits carbon for s little while when new, until the surfaces mate. This is clearly identified in the PSS docs. The vent hose allows air out.
Some of the older ones did not have the fitting, and you would do well to upgrade it when you're replacing the bellows.

SG · Oct 1, 2017

As I understand it, the issue has to due with ozone and other atmospheric degradation of the neoprene bellows. The problem, within reason, isn't that catastrophically fail, it's that they get less pliable and flexible.

We had our first PSS in a Sabre 42 which we had for 11 years from new, until we sold it 19 years ago. It worked flawlessly.

The second PSS was on our current boat, which we used during the 15 seasons without incident. Then, out of an abundence of caution I asked our mechanic to replace the bellows. He said that was reasonable (given the age and that we use the boat a bunch of hours each season); however, he pointed-out that it's not that much more to just replace the unit vs. the rebuild-kit. In light of the rigmarole in pulling the shaft, it seemed okay to spend the extra $200 (or so) -- I said, "it owed us nothing after 15 good years.)

I won't bore you with the story, but about 60 nm off of Cape May on my way to the outside of Nantucket toward Maine, I started to learn i) what happens when the "donut" comes loose enough to slide too far forward; and, ii) how, you can avoid it; iii) build your skills and avoiding panicking; and, iv) on how sailing back and arriving in Cape May about midnight reveals an amazing amount of drunken power boaters on their way out to somewhere :^))). We fixed our PSS -- which really wasn't the problem and still trust it with our lives.

P.S. - Our Sabre 42's and the original one on our J/160 didn't have a "vent tube". Our J/160 motors routinely at above 8 knots. The boat sail a bunch at between that and 9+ knots -- unless we're in lighter winds. We use the engine well over 100 hours a season. Unless you dry sailed a boat or hauled it a lot, I'm not sure the vent is all that necessary? If you have a PSS kit with one, it's really not been an issue -- the new one has that.

FastOlson · Oct 1, 2017

Meriachee said:
Part of the sealing methodology is having water against the mating surfaces. When the boat is in reverse, cavitation can force air up there and cause the surfaces to run dry. The carbon ring will wear when there's no water in there. It spits carbon for s little while when new, until the surfaces mate. This is clearly identified in the PSS docs. The vent hose allows air out.
Some of the older ones did not have the fitting, and you would do well to upgrade it when you're replacing the bellows.

You're not wrong, and I recall that there is another facet to fitting these things... while our model of boat has a shallow-angle shaft (and the shaft alley has always seemed to flood instantly when we launch), there are other boats with angles approaching the maximum of (about) 15 degrees maximum specified by some engine builders. Steeper that angle is, the longer the entrapped air would stay in the alley.

Good discussion, and while we may well already own our 'last' boat, if we did ever get another boat we would install a PSS seal if it did not come with one.

For whatever it's worth, we motor at 7 kts continuously with our 23 hp diesel.

Meriachee · Oct 1, 2017

I mentioned the water thing (I'm hesitant to say lubrication) because it's clearly stated in the docs.
The newer ones have a breather tube. More than one person, us included, have seen water coming in when the boat is in reverse, so there is some pressure in there, even at shallow angles.