Shaft Seal - PSS or Tides Marine Lip Seal ?

[Chief Engineer]

I think PSS are the better of the two.

I have seen a couple that "backed off" but that was about it.
I chalk that up to improper installation

[why me?]

hhmmmm... horses for courses...

I've heard of too many PSS seals backing off to chalk it up to just poor installation... I'm a pretty careful mechanic.. and I have never, ever been towed in, but it happened to me. I think the problem is they use stainless grub screws which aren't the hardness of normal such fasteners. Instead of tearing up the shaft by tightening, they tend to mash the head flat on the screws themselves..

A big advantage of the PSS is that your shaft surface can be wretched and it doesn't matter. If the stuffing box has left a gouge... irrelevant. The sealing surface is on the rotor. So instead of replacing the shaft, you can just replace the seal type.

Hey Main Sail... I set mine to 2 thou and that was OK.. keeping in mind I was using rubber cushed motor mounts and rubber cushed coupler as were standard for the Perkins installation. I have seen PSS seals suffer horrible misalignment and vibration and survive though. The Ruland gadgets looks great, better than my hose clamp for insurance. I would get one if I were installing another PSS.

I liked the PSS in spite of it's eccentricities.. because it was dry!! A big steel boat that was intolerant of standing water in the bilge.

This is a very good discussion. A reasonable skipper should be able to sort out the best alternative FOR THEIR BOAT from the various points of view here.

However for me... I'm putting outboards on my new boat..

Cheers

[Extemporaneous]

Well this little gem deserves a bump.

When I first got my boat (first/only boat) I was (still am) trying to learn about everything I could. Never sailed before and so I hired a Transport Captain/Instructor to help me bring my boat home (through 3 of the Great Lakes)(800Nm's). This is only to give you an idea of what I knew (NOTHING).
So I go into the Marina where I'm picking up the boat from and I ask them what they thought I may need in an emergency for the trip home. One of the items they mentioned that was additional to advise I had previously received was flax packing for the "stuffing box". I didn't know what size and so they sold me an assortment.
When I got home I searched and searched and read all about stuffing boxes. I could NOT find any "stuffing box" that looked like mine. After no success in my research I ended up leaving that and pursued the MANY other things (still am) that I had to learn. This Spring I put my boat in the water and I discover water is coming in from somewhere! By now I had read more about stuffing boxes and I didn't have one. I have a PYI PSS Shaft Seal and guess what??
Yes, the SS rotor backed off!!
It's odd to me that after all the searches (dozens) I did, this is the FIRST thread on any website that I've come across that talks about the SS Rotor on the PSS backing off!

Now the boat is out of the water for the season, I'm going to order the maintenance kit and change the bellows and other replaceables. That said, this seal has probably been in service since 1993! Less than 900 hrs on the engine/it though. And.... I will also be getting a Ruland split collar or similar!

So.......
CHECK your PSS collar and install a backup!

Best Regards,
Extemp.

P.S. Bids for the flax are starting at $25.00 ;-)

Originally Posted by Maine Sail

This is why in about 90% of the instances a solid coupling should not be re-used when you install a PSS or replace a shaft log hose. Re-using an old coupling or failing to have a new one properly fitted to the shaft then faced can potentially sink a boat or at the least ruin a shaft. Solid one piece couplings are fitted to a MAX variance between shaft and coupling of .001" per ABYC P-06 and SAE J756. Most shops will try for better than .001" which usually requires a light press or light tap fit. When you remove an old coupling the layer of rust that broke free is almost always more than .001"..

If a boat yard installs a PSS and does not also charge you for a new coupling and fit & face, and your coupling is a solid one, not split, please question this..


As for the PSS I now install Ruland split collars on every install. They are available from McMaster Carr and are cheap insurance.



Clamp Collar in use. Even if the set screws loosened up the stainless rotor is not going to slide up the shaft:



These set screws are a one time use item. If you need to adjust the stainless rotor and move it on the shaft you should also replace the set screws.

[delmarrey]

My theory for the seal ring backing off is;
The set screws used are SS but a bit softer then the prop shafts (usually an Aqualoy 19 or 22 these days). I noticed the hex socket will strip out if tightened too much. When one tightens down the first set screw and backs it up with a second ss it holds well for a while. But after many hours of operation/vibration the ss, being soft, mushrooms out allowing the ring to start moving under the load of the bellows. And of course the more it moves the worse it gets.

Occasionally, I reach down and give my ring a twist to see if it's loose but I do keep a couple wraps of painters tape behind the ring after discovering it a bit loose during a motor change. If it starts to back off the tape will show a wrinkle during my daily inspections. I've also bought (the special) extra ss's from PYI in case the hex strips again.

BTW-For now, my boat sits on the hard 10 months out of the year and when doing the change out I noticed pitting in the ring, probably from lack of use (lack of oxygen). I put a magnet on the ring and it is slightly magnetic, which makes it a poor grade of 316 SS. I had to machine .005" off the face to clean it up.
So my suggestion is, if you have long periods of storage, that one either back off the ring while on the hard or run your propulsion system on a regular schedule.

I've been thinking of making a new ring of 316L but I'll call PYI first to see why they use a lower grade of SS.

[Extemporaneous]

Okay........ But what's your bid on the flax?

Originally Posted by delmarrey

My theory for the seal ring backing off is;
The set screws used are SS but a bit softer then the prop shafts (usually an Aqualoy 19 or 22 these days). I noticed the hex socket will strip out if tightened too much. When one tightens down the first set screw and backs it up with a second ss it holds well for a while. But after many hours of operation/vibration the ss, being soft, mushrooms out allowing the ring to start moving under the load of the bellows. And of course the more it moves the worse it gets.

Occasionally, I reach down and give my ring a twist to see if it's loose but I do keep a couple wraps of painters tape behind the ring after discovering it a bit loose during a motor change. If it starts to back off the tape will show a wrinkle during my daily inspections. I've also bought (the special) extra ss's from PYI in case the hex strips again.

BTW-For now, my boat sits on the hard 10 months out of the year and when doing the change out I noticed pitting in the ring, probably from lack of use (lack of oxygen). I put a magnet on the ring and it is slightly magnetic, which makes it a poor grade of 316 SS. I had to machine .005" off the face to clean it up.
So my suggestion is, if you have long periods of storage, that one either back off the ring while on the hard or run your propulsion system on a regular schedule.

I've been thinking of making a new ring of 316L but I'll call PYI first to see why they use a lower grade of SS.

[delmarrey]

Originally Posted by Extemporaneous

Okay........ But what's your bid on the flax?

Sorry, but I'm trying to unload a couple stuffing boxes. I'm willing to take a decent offer.

[JayH]

Now it seems like more than coincidence that PYI carries these split collars on their website.

http://www.pyiinc.com/index.php?section=src&action=main

Originally Posted by Maine Sail

As for the PSS I now install Ruland split collars on every install. They are available from McMaster Carr and are cheap insurance.

[Mark Johnson]

My PSS rotor has also slipped once! The above collar as a back up, is a great solution, however a standard doughnut shaped shaft zinc will also work. Mine has been doing its job for 14 years now! I still like the PSS seal. It has otherwise worked perfectly for me. Mark

[Blue Stocking]

2 high quality hose clamps, 180* opposed, tight against the collar.

Mark, very nice tie-in for that shaft brush

[osirissail]

One - Tides - uses a "lip seal" which in my experience is not very good for long term use. The lip seal wears and also wears a ring into the prop shaft. Any vibration will promote rapid wear in a lip seal.
- - The other - PSS - uses the tried and true "swimming pool pump" shaft seal system of rotor and ceramic style face seal. I use the PSS and for 20 years it has worked fine. Maybe every couple/five years I will reset the face and wash away the worn down black powder worn off the ceramic face. It does spray the black powder dust to the sides around the assembly. I neglect it terribly and it still does not leak.
- - But as another has said - proper installation is paramount with either system. In the case of the stainless steel "disc" of the PSS, I marked the location of the set screws as they met the shaft and then countersunk the shaft a little bit so that the set screws were "into" the shaft a small amount. That eliminates the tendency of the set screws to "slip" on the shinny. smooth surface of the shaft.
- - I also use a collar just forward of the PSS assembly like Maine Sail posted to be an emergency back up should the shaft coupling and everything else fail to retain the shaft in the boat. I also put one on the rudder shaft just above the lower bearing to keep the rudder from dropping out of the boat should a failure occur.
- - It is critical that you get the proper model PSS system - one for low RPM and the other for high RPM with the vent tube.

[Mark Johnson]

The hose clamp idea occured to me, but here is my theory. These rotors have "grub screws" of a softer SS than the shaft. (mine is Aquamet 22) The sharp edge on the cup of the screw rounds, and then little by little the rotors wiggle themselves up the shaft from the pressure created by the bellows.
The opposing force to resist this creep, needs to be 100% uniform, so the rotors don't wobble, creating a small but constant "neusance leak". On my doughnut zinc, I put a small bead of caulk right down the middle of the face, put the halves together, and very gently slid it down untill it barely touched the rotor. (If I need to move something, all I need is a razor blade to cut the caulk).

Now IF the rotor wants to slip, it has uniform resistance. The slick SS version above would work the exact same way. (just cost more)

The screw box of a hose clamp would touch first, introducing a side load...

Sounds O.C. I know... Anyway, I haven't touched mine again in 14 years, although my thrust bearing is really easy on ALL shaft seals, as the shaft doesn't move with the engine at all, it only spins... Mark

[Mark Johnson]

One other thought. They no longer recomend the NON irrigated low RPM version. I switched mine over to the vented. Otherwise, if you launch after a haul and forget to "burp" the rotor right away, the air seal at the top of the stern tube can keep the water away from the rotor and FRY it..

Forgetting is easier than you'd think. When I launched our half built tri after 5 years of construction, in my excitment I forgot to burp the rotor, and fryed it right away. Once the surface has ANY flaws, they will drip. After changing to the High speed irrigated version and back up zinc, no more problem!

Be SURE to plumb up the irrigation hose AFTER the engines cooling water up turned loop, and that the loop is well above the WL. I also have a shut off valve, in the PSS vent hose, in case I need it.

These are a bit fiddely gadgets, but I prefer "the devil that I know". The works are out in the open and available for close inspection. Mark

[Extemporaneous]

Thanks Mark.
I thought?? that when using the high speed version with plumbing tube in a low speed situation (<12knots), one didn't need to plumb it to a water source, just to above the waterline to become a vent.
No?
Extemp.

Originally Posted by Mark Johnson

One other thought. They no longer recomend the NON irrigated low RPM version. I switched mine over to the vented. Otherwise, if you launch after a haul and forget to "burp" the rotor right away, the air seal at the top of the stern tube can keep the water away from the rotor and FRY it..

Forgetting is easier than you'd think. When I launched our half built tri after 5 years of construction, in my excitment I forgot to burp the rotor, and fryed it right away. Once the surface has ANY flaws, they will drip. After changing to the High speed irrigated version and back up zinc, no more problem!

Be SURE to plumb up the irrigation hose AFTER the engines cooling water up turned loop, and that the loop is well above the WL. I also have a shut off valve, in the PSS vent hose, in case I need it.

These are a bit fiddely gadgets, but I prefer "the devil that I know". The works are out in the open and available for close inspection. Mark

[CAELESTIS]

Thanks for the Rutland clamp idea. I have been using a t-bar style hose clamp. The rotor had slipped so many times, I had zero confidence in it.

[AnchorageGuy]

I have installed lots and lots of the PYI seals and have always used just a donut zinc, including our own, DSC02739a.jpg (image) . Chuck