PYI Dripless Seal issues

[Achernome]

We have had repeated problems with our Dripless seal on our 48' Sunward Ketch. Each year in Maine (and several times in Florida Bay) we have wrapped lobster/crab pots resulting in a sharp tug that pulls the engine back and resets the position of either or both of the Rubber spring loaded sleeve on the shaft log and the Metal disc that is fastened to the shaft. This has on two occasions resulted in near foundering of the vessel due to unrelated bilge pump issues.


Even with the addition of a sharktooth disc to the shaft near the propeller, the tug was sufficient to move these enough to cause significant leakage when the motor was at full power in forward gear. This summer I had the Engine mounts replaced with heavier mounts and I had the PSY seal Professionally reset in Maine. After the run south to Port Washington, we again had leakage without even snagging a pot. On inspection, it appeared that the inner set screws were not tight on the SS Disc and were, in fact rounded on the bottom to match the Shaft radius. We have replaced these set screws but have not had much engine time since to determine if the are holding.

Has anyone else had these issues and how have you addressed them?

[Paul L]

Sounds like you've had some real trials with this. A couple of comments:
1. The set screws are not supposed to be reused, so the replacement with new is good
2. We added a stainless split collar onto the shaft as a backup. They are available from McMaster Carr. Pic attached

[Delfin]

Originally Posted by Paul L

Sounds like you've had some real trials with this. A couple of comments:
1. The set screws are not supposed to be reused, so the replacement with new is good
2. We added a stainless split collar onto the shaft as a backup. They are available from McMaster Carr. Pic attached

We added something similar by way of a backup as well.

[nicholson31]

These seals work great when properly installed, mine has been eight years with no issues. In addition to the back-up collars as mentioned, seems like your the ss collar is either slipping back or there is not enough pressure on the carbon seal.
you may want to slightly compress the ss collar against the carbon sea another few mm, I believe installation usually calls for about 25 mm ("1" inch) from neutral. Yes and make sure you use ss Cupped set screws and double stacked.

[Toccata]

A question for our engineers about the effectiveness of double screws:
The outer grub screw threads are binding on the "back" of their threads and the inner screw is being pushed against the "front" of their threads.
Does this system actually increase the friction stopping one or both of the screws backing out (loosening off pressure on the shaft)?
Would it be better with one longer grub screw, with the load on one side of its thread over the whole length of the screw and a thread locking glue (Locktite)?

[nicholson31]

I wouldn't over think the engineering principles. Two set screws is simple, much like a back-up jam nut, plus easy to remove and install. Start applying lock thread and I can see the allen key head becoming blocked and/or stripped heads occurring. In this configuration you can Swap them around and be used as a spare set, providing you don't tighten down too hard on the backup set screw and damage the cupped edge.

[Jeanneau 45.2]

PYI instructions explicitly state to use the double stacked set screws provided with the kit (and replacements also available from PYI at a fair price). The instructions also state to not reuse the set screws. Who am I to second guess the designers?

[S/V Alchemy]

Originally Posted by Paul L

Sounds like you've had some real trials with this. A couple of comments:
1. The set screws are not supposed to be reused, so the replacement with new is good
2. We added a stainless split collar onto the shaft as a backup. They are available from McMaster Carr. Pic attached

Depending on the amount of shaft available and the nature of your cutlass bearing (if present), you can also use a split-collar zinc or even a hose clamp for this. But I find it odd that your shaft is so easily drawn back without damaging the prop. Perhaps you need a sort of cage around it, or a solid thrust-bearing inside the boat. We have a steel boat with an Aquadrive CV, a strong thrust bearing and the PSS behind that. Aside from "burping" it at launch, we have had zero ingress. But we also have the shaft coming out of the deadwood at the end of the full keel, a Shaft Shark line cutter, and a four-bladed, feathering prop, all factors when either keep the issue from happening, or allow it to fix itself before radical damage is done. So you may need a "systems approach" to solve this for your vessel. Here's a picture:

[sailcrazy]

We, too, have has some slippage issues with our PYI drippless. After a couple of phone calls to PYI, we bought new set screws.....and have not had that issue since! We also added a collar in front....we now use a readily available zinc collar, before that we used a shaft zinc....both do the job off backing up the set screws but the simple zinc collar has a flatter end (more bearing surface) and is less rotating mass.

[sailcrazy]

Sorry....forgot to mention that we also take some wet-dry sandpaper, slip it between the SS rub block and the carbon block, and rotate the driveshaft 10-15 times by hand (holding the sandpaper in place). That puts a new face and resurfaces the carbon block; we do it every year or two, just to ensure a good, flat surface on the carbon block. No leaks!

[doug cusick]

i don't trust set screws when there is no dimple on shaft to match. after compressing bellows properly i put a hose clamp on shaft in front of stainless disc to keep it from moving. no issues in 10 yrs of liveaboard cruising.

[a64pilot]

There is something called anti sabotage lacquer or slippage mark.
It can be as simple as some fingernail polish or any thicker paint you have laying around.
Just put a stripe between the two parts that are supposed to not move and if it does the paint mark will be broken and you’ll know right away.

Logically an automatic center punch should make enough of a mark for a set screw to grab onto.
Position the collar with one set screw holding, pop the center punch, install set screw, remove the first, pop center punch, put new set screw in?

[Toccata]

Without over thinking this (but I usually do), I do wonder further about the double grub screw problem...If the inner screw is well grounded/seated on the shaft, and then another screw is driven onto it, I suspect that the threads of the inner screw are effectively loosend from engagement with the female thread of the SS ring. (ie not touching either the back or front of the adjacent threads) So the only binding threads are indeed on the second or back screw.
Not all manufacturers get it right every time.
Warning, thread wander coming: Many people with screw retained crowns on dental implants will suffer screw loosening in time. A system that "shouldnt" fail but does.

[a64pilot]

As posted earlier, second screw is the same, and nothing more or less than a locknut.
A time honored tradition of keeping things from not loosening up.

[sazarac]

Originally Posted by Achernome

We have had repeated problems with our Dripless seal on our 48' Sunward Ketch. Each year in Maine (and several times in Florida Bay) we have wrapped lobster/crab pots resulting in a sharp tug that pulls the engine back and resets the position of either or both of the Rubber spring loaded sleeve on the shaft log and the Metal disc that is fastened to the shaft. This has on two occasions resulted in near foundering of the vessel due to unrelated bilge pump issues.


Even with the addition of a sharktooth disc to the shaft near the propeller, the tug was sufficient to move these enough to cause significant leakage when the motor was at full power in forward gear. This summer I had the Engine mounts replaced with heavier mounts and I had the PSY seal Professionally reset in Maine. After the run south to Port Washington, we again had leakage without even snagging a pot. On inspection, it appeared that the inner set screws were not tight on the SS Disc and were, in fact rounded on the bottom to match the Shaft radius. We have replaced these set screws but have not had much engine time since to determine if the are holding.

Has anyone else had these issues and how have you addressed them?

Almost sank because a loose can rolled into the rubber bellows and displased the seal. Took it out the net haul and replaced with a packing gland. I would never trust such a flimsy thing.