PSS Dripless Shaft Seal - venting hose?

[Chris Reinke]

I had a reputable yard add a PSS Dripless Shaft Seal at the end of last seasons when I replaced my stern tube. The yard advised me that the water supply line is only needed for vessels exceeding 12 knots, which I confirmed on the PSS web site. Apparently over 12 knots causes a vacuum and draws the water out of the seal, so a water supply is needed to ensure lubrication. However, the installation instructions also suggest a vent hose on boats under 12 knots to allow excess air to escape the stern tube and PSS bellows.

My concern is that the yard did not install a vent hose either. The barb for the vent was replaced with a bronze screw plug. The yard manager, who I have found to be very knowledgable in the past, said the vent was not needed with our lower RPM shaft, and slower hull speeds. He specifically said not to install it as the vent just represented another potential failure point.

So...here is my question. Has anyone else installed a PSS without a vent hose, or heard of such a recommendation? I know I need to "burp" the stern tube once the hull is launched to eliminate air in the tube, but after that I was told it required no maintenance.

[mgphl52]

Hi Chris,

KAYLA had a PSS dripless seal for over ten years with no vent hose and no problems. However, I did remove it a few years back as the bellows were getting to the end of their life expectancy and I wanted to install a drive saver. The dripless did not leave enough room for that in my CD28. So now I'm back to a standard packing nut that needs adjustment every so often, but I don't mind. I figure it would leak a lot less than the dripless if the bellows were to fail.

But hey, I also believe in loose-feet and free-wheeling...

-michael

[Doug Gibson]

Hi Chris -

I had a PSS Shaft Seal installed on my previous boat (Pearson 28), with no vent line and it worked fine for 15 years (replaced billows once). Besides 'burping', my theory was that any air trapped inside would find it's way out from static water pressure. The seal is provided by a thin layer of water between the stainless donut on the shaft and the carbon donut in the bellows. It forms a water tight seal, but not an 'air-tight' seal.

From my experience, I believe you'll be fine.

Doug

[Ron M.]

I installed a PSS a few weeks ago.......along with the vent hose. It took a half hour..... maybe.
From what I read and have been told, it will insure that water will get to the seal and burping isn't necessary.
Also, if you run the engine and engage the transmission while on the hard you can stick a funnel in the vent hose and add a little water to keep the seal from over heating. Having recently replaced the entire drive system I think it was easy insurance.
________
Edsel Villager

[Doug Gibson]

Rich - I will definitely check the bleeder screws to see if thats the source of the lead (wouldn't that be nice!). In the 3 years I've owned the boat, I haven't had to bleed line at this point, so no idea if they are loose.

Jeff - Additive sounds prudent to add. I believe the boat sat dormant for quite a while before a pruchased it. I've added about 50 gallons of 'new' diesel, so it's probably near 100% low sulfur at this point. Any specific brands you recommend?

Russell - your suggestion to consider pulling the engine next winter is very tempting - for all the reasons/tasks noted. I repacked the stuffing box during haulout a couple months ago... and I came very close to doing just that. The engine has very few hours on it, so taking care of the hygene and major maintenance items you described would give me another 5-10 years on this engine.

It will be a few weeks before I get back on the boat. I'll update the post once I confirm the leak source and fix.

Thanks for all you inputs.

[Doug Gibson]

Whoops... .thought I was updating a different posting. Please disregard.