Dripless Shaft Seal and other Issues (20-minute video)

[Christian Williams]

Choose "Watch on YouTube."

Dripless troubleshooting, Ray wheel pilot fix, installation of galvanic isolator, sail cover revision.

"Why plumb a sailboat's PSS to a thruhull and hose, when that is not necessary for vessels that don't go fast, like motorboats? Of the three options for PSS installation on sailboats, why choose that one?

"Option 1: no PSS plumbing. Burp unit by hand every launch. However, failing to burp the seal can cause it to burn out. Owners have to be responsible, especially of boats hauled often. They weren't. So "protection" was recommended.

"Option 2: Vent the PSS with an air line, essentially vented loop. This keeps water in the unit all the time and requires no thruhull. However, such a vent hose must rise above the max waterline when heeled. Usually a cable tie used to keep the end of the vent up at cockpit level . However, cable ties fail over time. If such a vent line falls below the waterline, the PSS floods the boat.* According to second-hand conversation with PSS, half a dozen boats were sunk that way, causing service bulletins. Enter Option 3.

"Option 3: Thruhull and irrigation line. This was considered "safer in the long run," because it guarded against owner failure to burp or inspect. And because access is often or usually difficult for shaft seals, especially, I am told for motorboats, and boats with V-drives.
Therefore, PSS for a while recommended all installs use thruhulls and hose to a fitting on the stator.

"Things are less clear-cut today, I am told, and all boatyard policies have drawbacks."

Also indexed in Thelonious blog Table of Contents

*Possible solution in Post #8 here.

 

[Loren Beach]

Thanks for a good video - education plus entertainment.
It's been several decades since I spoke to a PYI rep at the Seattle Boat Show (late 90's) and he explained that they were transitioning to having only one model, with a vent hose, rather than two models. Their "displacement hull model" which we still have does not have provision for a hose at all. Their vented model, intended for power boats that motored at 12+ knots, could suck water out of the shaft alley, and evidently needed water injection by some means.

As for the problem of our launching and retaining air in the shaft alley, that would be affected by the down-angle of the drive train. I note that some sailboat engine suppliers have stated that the max angle for their engines should be about 15 to 18 degrees, to avoid lube problems with the engine itself. And, some engine suppliers have a transmission with a built-in angle downward for the output shaft to further avoid/solve any install/design problem.

My surmise for having zero problems for air entrapment with our own boat is that out engine sits at a fairly 'flat' angle, and the shaft alley does not easily hold any air. Even less chance for this problem in any boat with the engine located further forward, like models with the engine under the galley or settee.

As the stock engine location, with conventional shaft, is/was designed to be further back toward the stern, the dreaded "down angle" would increase, I betcha.

Historical Trivia: All this is/was further exacerbated by builders constantly seeking ways to enlarge interior cabin floor space, as sailing was geared towards new customers in the 70's and 80's, and going forward. A different solution used was the V-drive, and EY installed that in their 70's 34 footer. (Along with models of Cal, Valiant, Niagara, and probably some others.)
Nowadays we have the near-ubiquitous Saildrive, moving the engine way back but also providing (IMO) scary ways to experience underwater aluminum corrosion & destruction.

Again, great video!

 

[Nick J]

Did you ever find out what was wrong with the thru Hull? What kind was it?

 

[Christian Williams]

The yard didn't save it for me (as usual). I've heard from several people saying they fail often in home installations. The boat mechanic said to me, "the ball is held only by a piece of metal, easy to corrode off." Somebody else commented that salt water in the line between metals of valve and dripless causes galvanic corrosion, which, who knows? It seems absurd, total failure in two years.

I've tried to identify it, but there are scores of such valves and they vary a lot in price. Remains a mystery.

There is not enough room on the stem for two hose clamps, which is an issue when below the waterline. The dripless barb does have sufficient room, and should have had two hose clamps.

 

[Nick J]

That's crazy, good catch on a lot of levels. It wouldn't have fixed your issue, but for those reading this later, TrueDesign thru hulls are a great option. No metal parts, strong enough to meet ABYC standards, and relatively easy to install.

This thread and others like it are really interesting. I've had great experience with PYI, so I'm surprised they would offer plumbing the vent to a thru hull as an option. I took a look at the install instructions, and they don't explicitly explain it, but there's a bit of additional info in there (from the high speed install section my comments in blue)

For high-speed vessels it is required that a water supply be plumbed to the PSS for the purpose of cooling and lubricating the seal faces (i.e., at over approximately 12 knots of speed a vacuum is created in the stern tube and water is drawn away from the PSS resulting in a loss of cooling water that may cause the carbon to over heat). There are multiple sources of water for the supply. The following are a few nonexhaustive examples. These are examples only and they may or may not apply to your particular boat. Note:
• Maximum water pressure should not exceed 10 PSI.
• T-off the engine raw water-cooling line. (Note: T-kits are available separately from PYI Inc for internal hose ¾”, 1” , 1¼”, 1½”)
This seems like the best option since it uses the raw water pump to force water into the seal, but as my neighbor boat found out, you need to be careful not to let the raw water plumbing hoses fall below the waterline when the pump is removed.
• Thread a barb fitting into the drain plug of the heat exchanger if applicable.
• Thread barb fitting into the drain plug of the exhaust manifold if the manifold is raw water-cooled.
(these two are kind of the same solution as above, just a different take-off point)
• Add a small scoop under water for keel-cooled boats or T-off another water pick up. (Note: A valve must be installed to regulate the water flow as too high water flow may over pressurize the PSS seal). Use an appropriate “underwater rated” hose from the fittings on the boat and the fitting on the PSS and secure them with two (2) hose clamps at each end, as required by U.S.C.G. regulations.
This is where it get's interesting and where I'm assuming your installer took their idea from. The main difference is our boats don't go over 12 knots so the vacuum isn't formed and now water, and trapped air, is pulled from the shaft log. They also mention using a scoop which would force the water in instead of pulling it out.

The note on a valve is also interesting. I don't think I've ever seen a valve between a dripless and the raw water system, but it sounds like a good idea if you have a fast boat and used this install method.

The instructions are a little confusing when they say: Sailboats or displacement powerboats with a powering speed below 12 knots can use either method A or B, but the options are listed as 15.1 and 15.2 and 15.1 (I'm assuming this is option A) is labeled "Low Speed Boats".

 

[Loren Beach]

The instructions are a little confusing when they say: Sailboats or displacement powerboats with a powering speed below 12 knots can use either method A or B, but the options are listed as 15.1 and 15.2 and 15.1 (I'm assuming this is option A) is labeled "Low Speed Boats".

Rather insulting! (Referring to us as owning Low Speed Boats! We like to think of them as Fast!)
Harrumph....

 

[tenders]

Option four: go back to an old-school stuffing box after 25 years of low-grade annoyance with the shaft seal design, and one incidence of high-grade annoyance which was the tipping point. The stuffing box fails gradually, and can be serviced indefinitely without removing the shaft until the ridiculously thick shaft log hose wears out after many decades.

The advertised “dusty bilge” benefit never materialized, and I found myself pulling my shaft out every 5 years to deal with the seal. Getting the shaft off the coupling was a huge access pain, the most onerous job on the boat, with my Atomic Four vee-drive setup.

 

[Pete the Cat]

Option four: go back to an old-school stuffing box after 25 years of low-grade annoyance with the shaft seal design, and one incidence of high-grade annoyance which was the tipping point. The stuffing box fails gradually, and can be serviced indefinitely without removing the shaft until the ridiculously thick shaft log hose wears out after many decades.

The advertised “dusty bilge” benefit never materialized, and I found myself pulling my shaft out every 5 years to deal with the seal. Getting the shaft off the coupling was a huge access pain, the most onerous job on the boat, with my Atomic Four vee-drive setup.

And option 5.5: learn to clean and pack your stuffing box yourself for your own protection and pack it carefully with GTex and the clay stuff and forget it. I have been doing this for 30 years after being schooled by the lobstermen here in Maine. It takes a bit of break in attention (follow the directions), but I have not looked at it in 10 years and more than 1000 hours and it doesn't leak. if something happens, I have a spare set of rings and I can repair or replace it anytime any place. As I have said before, I understand why the boatyards like PSS seals. They do not want to send neophytes from the boatyard with something they have to break in and adjust and if it breaks down 4 or 5 years from now it is clearly not their fault. I am sure they have a legal warning in the packing materials that tells you that you should have it serviced every few years.