PSS Shaft Seals

2011 February 28
by Chris Brown
PSS Installed

PSS Seal Refreshed and Ready to go

PSS Seals are found on many of the pleasure yachts.  The PSS Seal system is a “face” seal that relies on the pressure between a carbon face stationary to the stern tube and a stainless steel face on the ring installed on the shaft.

Maintenance on these seals is pretty straightforward.  If the shaft is out we will usually reface the stainless steel ring in our machine shop.  A smooth, flat face, free of debris, is required for a solid seal.  The carbon face is inspected for chips or cracks.  If cracked they must be replaced.  Finally, we inspect the bellow hose for cracks or other signs of wear.  The bellow hose acts as a compression spring to keep the carbon against the stainless steel.  If the bellow hose is aging, it will lose the spring effect and not apply enough tension.  This is sometimes noticed if the seal leaks when throttling up the engines.  Depending on the engine mounts, the engine will shift forward under prop load which eases the pressure between the stainless steel and the carbon.  If the bellows is not compensating then leaking will occur.  PSS recommends replacing the bellow hose every seven years.

Finally, during installation the stainless steel ring is compressed a distance, per the PSS manual (it varies with shaft diameter).  Notice in the picture the sharpie mark on the shaft showing the position of the ring in the neutral state prior to compressing the bellows.

PSS Seal are very effective and easy to maintain.  Give us a call if you have any questions or concerns with your shaft seal system.

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