Your favourite (or least favourite) shaft seal.

[GILow]

Hi all,

The new boat is getting a new prop shaft. So, it’s time to consider whether to stay with the traditional stuffing box (currently fitted) or go with one of the many other options.

I will have a brand new 1.25” prop shaft, access to the seal is about as good as you could possibly ask (just lift a panel in the aft cabin sole and it’s right there, just inches below the sole.)

Shaft rev range is up to 1350 rpm max. Maximum boat speed under engine would be about 7.5 knots.

Boat is fibreglass so a dry bilge is (in theory) a possibility.

What would you install, and why?

Matt

[Nekton73]

I've only ever lived with a standard flax packed stuffing box. It's easy to inspect, adjust, and sop up the small amount of water that results from the slow leak as long as I keep on top of it, which I do. I have easy access to the low point in the bilge where it collects, which helps a lot.


I have sailed boats with dripless stuffing boxes. They work great. Inspect the bellows religiously and replace at recommended intervals and you should be fine.



No doubt there are horror stories about both options.



My stuffing box is one of the least terrifying items on my boat.

[skipperpete]

I’ve been shipmate with just about all of them and the only one that I absolutely dislike is this one. The rubber bit is just to fragile and tears easily, the bit clamped onto the propshaft fails miserably and the hose clamps eventually end up damaging the soft “ bellows)[ATTACH]267268

[stormalong]

PSS on my boat since new - 37 years. I had some problems with overheating until at PYI's suggestion I installed the high speed option. It draws in water to prevent an air pocket. A bit more plumbing but worth it.

[GILow]

Originally Posted by skipperpete

I’ve been shipmate with just about all of them and the only one that I absolutely dislike is this one. The rubber bit is just to fragile and tears easily, the bit clamped onto the propshaft fails miserably and the hose clamps eventually end up damaging the soft “ bellows)[ATTACH]267268

Actually, that looks rather horrible. What is it?

[Celestialsailor]

I had used the flax type from the beginning. There was no there option. Then some slick Willie sold me on the idea of Teflon packing. It either ran sizzling hot or trying to losen it slightly let too much water in. The next haul out, I went back to the trusty flax.

[Fore and Aft]

Gilow I have been using one of these for six years and love it. If every old steel yacht, I surveyed had one of these there would be a lot less rust in the bilges.

Cheers
https://www.shaftseal.com/pss-type-a-seal.html

[skipperpete]

Haha, the manufacturers had so little faith in the bellows they included an anti sinking device (the red tag) that clamps a rubber seal tight on the prop shaft in case the bellows fails BUT this lifesaving device renders propulsion un available and it gets worse...... if you’re sailing fast and can’t lock the propshaft the whole assembly can be torn off the stern tube. Sorry Fore and Aft, I’ve seen too many problems with these to give em a tick.

[Wotname]

3 boats, 3 traditional stuffing boxes and 3 PYI, PSS type A shaft seals.

I guess there is nothing wrong with a traditional stuffing box but I am lazy and love the set and forget aspects of the PSS (plus the dusty bilge). Only maintenance was replace the bellows at the recommended interval (5 or 10 years from memory).

[Wotname]

Originally Posted by skipperpete

I’ve been shipmate with just about all of them and the only one that I absolutely dislike is this one. The rubber bit is just to fragile and tears easily, the bit clamped onto the propshaft fails miserably and the hose clamps eventually end up damaging the soft “ bellows)[ATTACH]267268

Originally Posted by skipperpete

Haha, the manufacturers had so little faith in the bellows they included an anti sinking device (the red tag) that clamps a rubber seal tight on the prop shaft in case the bellows fails BUT this lifesaving device renders propulsion un available and it gets worse...... if you’re sailing fast and can’t lock the propshaft the whole assembly can be torn off the stern tube. Sorry Fore and Aft, I’ve seen too many problems with these to give em a tick.

Any idea who made that thing? It looks nothing like a proper PSS type seal like F&A linked.

[stormalong]

Originally Posted by skipperpete

Haha, the manufacturers had so little faith in the bellows they included an anti sinking device (the red tag) that clamps a rubber seal tight on the prop shaft in case the bellows fails BUT this lifesaving device renders propulsion un available and it gets worse...... if you’re sailing fast and can’t lock the propshaft the whole assembly can be torn off the stern tube. Sorry Fore and Aft, I’ve seen too many problems with these to give em a tick.

Never saw anything like that on a PSS. Can you show your source of this revelation. Been using one on my boat since 1990. See my post above.

[Jim Cate]

That device is a ManeSeal. We've had one for almost 20 years now, and have found it pretty reliable. Replace every 7-9 years per vendors advice. Only trouble has been one failed when it got whacked hard by a unsecured bin door, right in it's only delicate spot... bad luck but the boat didn't sink!

IMO the simple hose clamp that seals the bellows to the shaft is trouble free... more so than the complicated device on the PSS with its multiple grub screws and o-rings that people are always griping about slipping on the shaft.

Jim

[mvweebles]

Frequent topic on powerboat forums. There are two general types of dripless seals - a two-piece with collar attached to shaft with a stationary mating surface such as the PSS. The second being a lipseal style with stationary rubber-like seals around the shaft such as Tides (or the Volvo seals that get an honorable mention on this forum from time to time). The lipseal style has the benefit of being able to install spare seals on the shaft for easy maintenance when needed. With the 2-piece seal, shaft must be backed out (often pulled entirely depending on after clearance to rudder).

In my opinion, if you have good access to your stuffing box, and you're comfortable with maintenance of it, theres a lot to be said for traditional stuffing box. Newer GPO stuffing is the best and can be close to dripless. It's easy to maintain, but if it's intimidating, go with one of the above dripless styles.

Personally, after 20 years, I converted from traditional to PSS dripless simply because I aspire to a 100% dry bilge. I then decided to swap the PSS for a Tides lipseal style when I had some shaft work done even though the PSS had performed well for me. Why? I had seen a PSS failure due to improper install (collar slipped - easily prevented by putting a hose clamp behind it in addition to properly installing the double set screws). And I had seen a Tides leak after many years that was easily repaired with a standby seal. Finally, lipseals are very common and reliable types of seals - lipseals on crankshaft is what keeps oil inside an engine.

[Davidasailor]

8 years with our Volvo seal and not a drop of water in the boat. Only maintenance is adding a pea sized amount of grease and burping it once a year.

[rslifkin]

Standard stuffing boxes for me. With modern packing adjusted well, they only drip a tiny bit while running and rarely to not at all while stopped. IMO there are less failure modes that would require pulling the shaft to fix with a standard stuffing box. As long as the metal is intact and the big hose between the stuffing box and shaft log is intact, you can repack the thing in the water and be good to go.