Burping a PSS Dripless Seal

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Oct 5, 2007
One of the Nordic Tug owners was told that his interior cutlass bearing burned*out because they didn't burp the PSS seal after the boat had been out of the water. Certain years of NT's have a cutlass bearing just aft of the PSS where the long shaft enters the tube heading aft. The other one is just in front of the prop. The interior*bearing gets water from the PSS water feed*hose and from the outside via water coming up the shaft tube.

I am on my second set of PSS seals and have never heard this. Anyone know?
The PSS web site mentions "If the boat sits idle for a long period of time (generally 3 months or more),it is necessary to move the carbon face back to allow a small amount of water to enter the boat. "

I could imagine an airlock happening if there's a high spot in the water feed loop - if the boat doesn't get going fast enough to cause a suction on the outside to pull the air out, and if the airlock keeps water from coming in.

Mine are plumbed in with a pretty straight line from the PSS to the raw water inlet on the engine, so any air in there should vent right out.

But it would certainly seem prudent to give it a pull after launching.
I always*burp mine first thing after launch; never had a problem.* The surveyor mentioned this during my pre-purchase survey.

I thought most drippless have a small hose after the raw water pump side to the drippless to lubricate the front cutlass and/or the SS collar against the Teflon boot.* That is why they leak when turnings.* Also the boat when moving through the water will creates a vacuum so most of the water is sucked out leaving the front area dry.

Without the hose it would seem the area wold be dry most of the time when up and running.

PSS says in the installation manual that for boats running under 12 knots max speed (most of us), all that you have to do is to run the hose up well above the water line. This allows air to escape.

Faster boats can create a vacuum on the outside of the seal as the boat moves through the water. These have the hose connected to a seawater source - otherwise the vacuum could pull out the water and leave the seal & bearing unlubricated.
Not only did my surveyor tell me that it needed to be burped after a haulout but so did the PO.



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