Dripless shaft test

FastOlson · Oct 16, 2013

scott754 said:
At the Annapolis boat show I was talking to the designer of a beautiful Passport 50 and he did not like installing dripless shaft systems on his boats because if failure, it would be catastrophic. I have a dripless on my Catalina 350 with concern that there is no way of knowing if it is working properly. The manual states if you hear noises from the shaft you should break it down and rebuild. Perhaps a clear hose on the feed would show if is working. Any thoughts?

So, Bob Perry told you personally that he Doesn't Like the venerable PSS shaft seal?
That's interesting, and, unexpected.

Ours has been working faithfully since 1995. We've put in one new bellows, per advice from the vendor - and he admitted that they actually have a long life but their attorneys came up a shorter ("about ten years") number for a replacement, and overruled the engineers. Liability concerns (almost) always trump technology,

Loren

windward54 · Oct 16, 2013

If you are referring to a PSS, I had one on my last boat and never had a bit of trouble with it. And last I heard, the unit is still going great. I also knew a lot of people that had the PSS and it never caused any problems either. I like the unit and will be having one installed on my next haulout.

Rick D · Oct 16, 2013

Had Several Over 20 Years

I replaced my bellows twice at 1000 hours each. The old ones seemed perfect. There have been failures, most related to debris in the bilge getting caught, improper installation, failure to burp the bellows upon launch in the older models.

However, having said that, this discussion will simply be one of who knows whom that did or did not have a failure, personal experiences and hearsay. What really counts are the statistics. What is the failure rate of a dripless shaft seal vs. standard stuffing boxes. Your insurance company may have some numbers, but I doubt it since shaft seal failure of any type is a fraction of sinking claims. You could call the manufacturer. Most certainly, they have their number but not the other.

Ultimately, like Perry, it comes down to your comfort level. If you are not comfortable with them, I'd suggest replacement with a standard stuffing box next haul.

jsalley · Oct 16, 2013

I noticed while poking around the bilges of the new Catalina 355 and 385 in Annapolis that Catalina has changed from the PSS to traditional stuffing boxes. The dealer rep wasn't aware that they had made the change, and Gerry Douglas was tied up so couldn't ask him about it. I have the PSS on my 2006 C309 and have been quite happy with it (except doing a routine bellows change last year, which was a bear).

Scott T-Bird · Oct 16, 2013

Thru hull and feed? What am I missing. The water on mine comes thru the shaft log ... the only tube I have is the air-relief tube which makes it unnecessary to "burp" the bellows.

Rick D · Oct 16, 2013

Understand, but...

scott754 said:
It's not the PSS I dislike It's Lack of knowing if it is working. A blocked through hull would stop the cooling water and there would be no way of knowing of a problem.

....unless there has been a change, the PSS gets its water through the shaft log, not through any through hull. The line is a vent to avoid air blockage in the bellows which is why the old style had to be burped after launching.

Delezynski · Oct 16, 2013

I have to add to this thread a quick note.

First my disclosure, I do not have a PSS on our boat. My not installing one is due to my concern of a failure when in a remote area. BUT, if others want one, great. It's each captains choice. One of the best things about boating, we each make our own choices.

What I do dislike is the prevailing notion that only the PSS type shaft seals are “dripless”.

Back in 1999 or so I installed moldable packing in our standard shaft. I bought one kit, and still have half of it left. Since then, our packing has NOT dripped AT ALL! It has been truly “dripless”. And, at a fraction of the cost of one of the bellows type systems.

Before you jump, I check it often. After running at my rated RPM for more than an hour I can still hold my hand on the gland nut without excessive heat. I have removed my prop shaft a number of times and there is no excessive wear on it.

Just my 2 cents worth.

Greg

jsalley · Oct 16, 2013

The "vent" line does actually supply the cooling water on installations (like recent Catalinas) that have the Cutless bearing in a skeg, rather than in a hull-mounted shaft strut. Though some cooling water comes in around the bearing, it is insufficient to adequately cool and lubricate the carbon shaft seal, so the additional water from the vent line is required.

JK_Boston_Catalina310 · Oct 16, 2013

jsalley said:
The "vent" line does actually supply the cooling water on installations (like recent Catalinas) that have the Cutless bearing in a skeg, rather than in a hull-mounted shaft strut. Though some cooling water comes in around the bearing, it is insufficient to adequately cool and lubricate the carbon shaft seal, so the additional water from the vent line is required.

When PSS are installed on power boats they have a similar set up. The vent line is connected to the drain from the exhaust elbow typically. Something about the water not moving enough in the traditional setup to allow for proper cooling.

Benny17441 · Oct 16, 2013

Yes the failure rate is minimal and the performance and longevity exceed expectations but it is also a fact that when they fail they will do so catastrophically. Perhaps for a weekend sailor that would not be a big negative but for a circumnavigator or offshore cruiser that might be a huge liability. I for one appreciate the performance and forgiveness of a packing gland.

gettinthere · Oct 17, 2013

Bob Perry was at the show?

gettinthere · Oct 17, 2013

Nuts, I was at Passport on Monday!
He must have just missed me.