Propeller shaft seal does not seem right.

[JohnnyP]

I have 1984 29' Columbia with Yanmar 2GM. The propeller shaft is sealed with a Packless Sealing System (PSS) here: PYI Inc. | PSS Type A Shaft Seal

While working around the engine, there are times when the seal will leak from between the sealing surface of the stainless steel rotor and the black-colored carbon flange in the picture. I am talking about a small stream - not a drip. The black colored carbon flange has some play and I can move it back and forth about 1/4" in each direction. When I read the PSS website, it sounds like some play is built into the design to make up for misalignment. That is understandable. My problem is that I can move it over 1/8" and it will leak a stream of water until I physically move it back. Is that right? Seems off to me. Thoughts?

Bonus question: Take a look at the hose clamp above the stainless steel rotor. It is clamped directly onto the shaft. What could be the purpose of this? Should I be taking it off?

Thanks!

John

 

[arf145]

I think some owners put a clamp behind the stainless steel piece to ensure that it doesn't back off, though that one isn't up against it, so I don't know.

 

[marcham]

It looks over compressed. Where is the vent line? When was it last serviced? (Every 6 years ish parts have to be replaced.

 

[Captain Larry-DH]

It looks over compressed. Where is the vent line? When was it last serviced? (Every 6 years ish parts have to be replaced.

Agree, it appears to be over compressed. Time to take it apart and service it. PSS has good tech support - take it apart and take measurements so you can tell them how much compression was in use vs. uncompressed. You might also find pitting on the mating surfaces. Take photos. They will advise you. In many cases you can restore the mating surfaces by putting fine grades of wet sandpaper on a flat glass surface and honing them by hand. You can also get a new surface by reversing the steel disk.

 

[Ward H]

I agree that the clamp is being used as a marker to indicate if the collar is slipping forward and loosening the seal. It's not tight against the collar so you can watch the gap. If it closes you know the collar is slipping. My surveyor suggested this on my boat. I bought a SS split collar from McMaster Carr and installed it 1/8" back.

The vent is there to vent air from cavitation from being trapped in the shaft log and allowing the seal to run dry. Also when the boat is launched trap air can escape. This is more of a problem on power boats due to them running at much faster speeds and higher rpms. On sailboats with our slower speeds and rpms, it is not required to be hooked up.

The PSS seal on my boat doesn't have the vent. Be sure to "burp" the air out of the seal upon launch so it is wet.

That's the only time my seal lets in any water, when I burp it. The play in yours sounds about the same as in mine.

There is also a spec for how much the seal is compressed so it holds the proper amount of pressure against the matting surfaces.

Might be best to call PYI, send them the photo and ask their opinion. I showed them a photo of mine at the Annapolis Boat Show a few years back and asked how to tell when it should be changed out. I half expected to be told yep, time for a new one. Instead he told me how to examine the hose and seal, what would indicate time for a new one and that mine, from the photo, looked fine for several more years but examine it much more closely when I got back to the boat.

 

[dlochner]

The extra clamp on the shaft is a safety feature. If for some reason the SS rotor should come loose, it will not slide past the clamp. It should be snug against the rotor.

The engine looks misaligned and the bellows over compressed. When was the bellows last changed? They should be changed every 5-7 years. If the bellows needs replacing it is not that much more expensive to replace the whole seal.

The current crop of PSS have a vent line in the Graphite bearing to allow water to flow into the seal for cooling. The style you have requires burping the seal after launch. Burping can damage the graphite bearing which can cause it to leak.

If the seal was damaged or the engine misaligned in the shaft log, over compressing the bellows may have been an attempt to stem the flow of water from the seal.

There are good instructions on the PYI website and they support is excellent.

 

[Scott T-Bird]

@JohnnyP based on this post, you haven't really defined a problem. You say it leaks "while working around the engine." So does that mean it is leaking while the bellows is undisturbed or it leaks only when you disturb the bellows by pressing on it? Have you only discovered this leak while manipulating the bellows or did you have a chronic leak that was noticed when you saw water in the bilge but you did not discover the source until you noticed water leaking around the bellows? Is there leakage while the engine is off (and you are not touching anything) or do leaks occur only while the shaft is spinning (which is usually indicted by a spray of seawater)?

As others have said, the bellows do look over-compressed. If you move the bellows over (sideways), you are manipulating the bellows out of alignment and of course it will leak, but that's not to say it is out of alignment before you move it. If you can only press another 1/8" of compression, that would seem to indicate that the bellows is over compressed.

Be aware that if you back off the set screws to loosen the ss collar, you may not be able to re-use the set screws. I believe that they recommend that new set screws should be obtained if you move that collar. PSS doesn't even require the back-up clamp. If they did, I would expect them to provide it. My boat didn't have one until I installed a split collar as @Ward H described. Whether it is offset by an 1/8" or not shouldn't matter. I would agree with Ward that seeing a gap close might be a better warning. If the back-up ring was to be snug, you might not notice if there is movement. But the reality is, the collar should never move if the set screws are set properly.

 

[garymalmgren]

Time to replace the whole assembly.
Why?

I suspect the stainless rotor was originally in a position further forward (closer to the gear box), butted up against the clamp on the prop shaft.
At some stage the faces started to leak due to wear and then the rotor was pushed further back to meet the carbon stator (seal) with greater pressure.
Thus the compressed bellows.
Greater pressure mean faster wear.

RE: are times when the seal will leak from between the sealing surface of the stainless steel rotor and the black-colored carbon flange in the picture. I am talking about a small stream - not a drip.

This would indicate a spiral groove or track in the stator. Maybe caused by grit, sand or debris.
You need a stator and rotor and as noted the cost is not much more for the whole assembly, including a new bellows.

Gary

 

[Tally Ho]

The whole thing looks like it is misaligned to the left…look at the rotor/ceramic disk interface. Maybe it is an optical allusion, but it doesn’t look even across the interface.



Greg

 

[garymalmgren]

Re alignment of seal.
The stainless rotor is fixed perpendicular to the shaft with little clearance for miss alignment.
The stator is fixed to the bellows which gives enough to allow the stator to self align.
I think what you see in the photo is a distortion.

 

[dlochner]

Re alignment of seal.
The stainless rotor is fixed perpendicular to the shaft with little clearance for miss alignment.
The stator is fixed to the bellows which gives enough to allow the stator to self align.
I think what you see in the photo is a distortion.
View attachment 222295

Look at the angle of the shaft to the shaft log, the shaft is not aligned to the shaft log by a fair amount. Also look at the gaps between the ribs on the bellows, the gaps on the right are are larger than the gaps on the left further indicating a misalignment.

The flexibility of the bellows does allow for some misalignment, however I think the the misalignment here is pushing the tolerances. Thus, any additional movement in the bellows will allow a leak and the leak will be a stream, not a drip. I've been down this road when I removed my transmission while in the water. The bellows would flex enough to keep the seal, but it was tenuous, if the shaft moved even a few fractions of an inch the water would stream in at a high rate.

Do replace all the set screws with cup point set screws. They are metric, I can't remember if they are a 4mm or 6mm. PYI sells them, however you can buy a lifetime supply of them from McMaster-Carr for about the same money that PYI wants for a single set. Also use Locktite on the threads.

 

[RoyS]

I have had one of these seals for 18 years. Mine never had the vent hose and had to be burped every Spring launch. It never leaked and never needed to be burped after Spring. The lack of a vent hose should not be a problem for you. The original bearing still works without leaks with about 1,000 engine hours on it. The bellows are an issue, however. I replaced my first bellows after ten years only because PYS recommended replacement after four years. It still appeared to be in perfect condition and did not need to be replaced in my opinion. The replacement bellows displayed surface cracking after ten years. That cracking may have been caused by a diesel tank leak that I had at that time. The second replacement bellows, however, was different than the two originals. The spaces between the ribs were smaller. The instructions still said to compress the bellows one inch but this required excessive force to achieve. The comments above stating that your bellows appear over-compressed may be only because the later bellows design has changed. At the time I noticed the changed design and the excessive force required to achieve the one inch compresssion. I called, sent photos, and wrote to PSI, and even sent them one of the original design bellows for them to compare the differences. They declined to answer. I do not agree that they are a responsive company. My guess is that the newer design bellows are over-compressed (at one inch) and will not tolerate much mis-alignment between the shaft and the stern tube before causing the bearing to separate and leak.

 

[JohnnyP]

Thanks for all the great thoughts. I will follow up and let you know how it turns out. Scott T-bird, you were looking for more description of the problem. Sometimes when I lean on the Yanmar to get a better look at the seal system behind it, I move the engine a little and the seal starts to pour water. When I get off the engine, the seal does not reset without me reaching back there and jiggling it until it resets.

 

[Captain Larry-DH]

One more thing you need to know - if you haven’t installed or removed it - PSS uses 2 set screws per hole (stacked). So when you loosen or remove the first allen screw you should expect that there is another beneath it.

 

[dlochner]

Thanks for all the great thoughts. I will follow up and let you know how it turns out. Scott T-bird, you were looking for more description of the problem. Sometimes when I lean on the Yanmar to get a better look at the seal system behind it, I move the engine a little and the seal starts to pour water. When I get off the engine, the seal does not reset without me reaching back there and jiggling it until it resets.

The engine shouldn't move that much from your weight. Check the engine mounts, they may need changing. A broken or worn mount could change the engine alignment which would put pressure on the seal.