PSS Seal Problems?

[robbieg]

I've been looking at a boat with a PSS seal on a 1 inch shaft with a 30hp engine (sailboat aux). I know there has been some good feedback about these seals on the forum so I would be interested in veiws/experiences of forumites about 2 issues the owner mentioned before fitting one myself.

1. The owner normally frees his seal by hand if the boat has been unused for a few weeks because apparently the stainless steel rotor and carbon facing can seize together as the seawater between the two dries out and the salt crystals stick the 2 surfaces together. Since getting at the seal on my boat and freeing by hand is a fag I thought of simply turning the shaft by putting in gear to break the "seal" but am told is not a good idea since this puts a lot off rotational force on the rubber hose holding the seal to the stern tube. Anyone else any experience of this and any solutions.

2. Although the seal is apparently dry and robust I noticed staining on the s/s rotor and white salt deposits on the rotor. Since sea water lubricates the interface between the stainless steel rotor and carbon facing I suspect small amounts must find there way onto the seal and cause this-anyone able to confirm this is normal.

Generally the owner was postive about the seal and recommended it.

 

[Robin]

Unless the seal is fitted with a vent tube taken above the waterline or the same connection is used to feed water to the seal the seal needs to be 'burped' of air after a period ashore. Most new sailboat installations will have the vent tube (ours does) as I believe this is the only one being stocked as standard now. It is only high speed installations that need the waterfeed.

Ours has never stuck nor would I expect it too. Is the boat you looked at on a drying mooring perhaps?

 

[robbieg]

No its Marina berthed and it does have a vent tube. Interesting that neither of these issues affects you-possibly a seal adjustment issue? Interested in any other experiences of formites. I've tried contacting the manufacturers in the States about this but no response to date.

 

[CSFenwick]

Ours sticks if the prop shaft isn't moved for a week or so. When we’re on the boat I do a daily engine check and just give the prop shaft a quick turn by hand which releases it if it has stuck. Realistically you only need to do this once per trip as it does need a good few days before it sticks again. It doesn't stick particularly hard and it would come free when you put the engine in gear but I've heard a salty old sea tale of one on a MOBO that wasn't moved for 12 months. The story goes that it was stuck so hard that when the engine was put in gear the bellows tore which of course let the sea in. If it is true the seal must have been stuck far harder than I’ve ever known mine to be and the rubber bellows must have been old and quite brittle. Still, it focuses your mind on freeing it up by hand with the engine check rather than just putting the boat in gear. Must say I'm 100% happy with the seal which we've had for 2 years. This 'sticking' issue really isn't a big deal.

 

[biscuit]

The bellows pushes the carbon disc againt the steel disc: the bellows needs to be full of water to lubricate this interface. If accessible, the bellows can be pulled back easily (or squeezed), allowing seawater in. Dont use the vent tube for this. If inacessible, the vent tube can be connected to the raw water intake (with an antsyphon looop!!) to allow water into the bellows. Without the "spring" effect of the bellows the boat would sink. An alarming thought but apparently doesnt happpen...Provided the bellows are tweaked on relaunch & after drying out, a little visible seawater shouldnt hurt. As for the carbon & steel gumming together & tearing the bellows it doesnt bear thinking about!

 

[Roberto]

re sticking, I have a seal working with the same principle (though of a different brand) of graphite ring against a stainless steel plate: with the boat in the water it will not stick for up to about 6 weeks (never left the boat unused longer, so cannot comment on longer periods)

OTOH when out of the water (the boat winters for about four/five months) I always found the two surfaces sticking. They cannot be separated by hand, I insert a screwdriver blade between the steel plate and the outer graphite body and they are easily unstuck.

 

[Robin]

[ QUOTE ]
No its Marina berthed and it does have a vent tube. Interesting that neither of these issues affects you-possibly a seal adjustment issue? Interested in any other experiences of formites. I've tried contacting the manufacturers in the States about this but no response to date.

[/ QUOTE ]

My link to PSS USA wouldn't work so I did a search and maybe they are now handled by 'Spurs'? PSS Info You might like to email them with the question.

If you look at the design, the reinforced corrugated bellows is fitted with double clamps both ends so a momentary bit of in gear grunt would have little effect if some sticking occurred. Maybe ours has stuck, unless it made a noise I wouldn't know! However it has run some 6,000mls without a drop of water passing it and it still looks like new. The PSS bellows is a very tough one compared to the soft rubber one on the Deepsea/Manecraft seals and having had one which showed splits after just one season I'd not have another.