Dear Boat Doctor,

I just bought a new-to-me Beneteau 40 with a PSS dripless prop shaft seal. I appreciate the dry bilge, but those little set screws holding the sealing collar in place make me nervous. Am I worrying for nothing or should I do something to shore this up?

Dan Birkawitz

Boston, Massachusetts

Dear Dan,

It’s worth checking that the PSS shaft seal is installed correctly. The seal collar on the PSS is held in place with several set screws. These screws are set tight and they dig into the shaft. There is a detail that is sometimes missed: The set screws are backed up with another set screw threaded into the same hole. The concept is similar to double nuts on a threaded stud.

It’s a little bit of work to inspect that both screws are there, but well worth the 20 minutes to back them both out. Apply Loctite before you put them back in.

The traditional belt-and-suspenders approach to keeping the collar in place was to install a shaft zinc anode just forward of the collar. The collar was locked in place between the set screws and the tight fit of the zinc. The manufacturer has answered this need with a more elegant solution, the Shaft Retention Collar. This is a split collar that bolts around the shaft to very firmly lock things in place. You can find them at www.shaftseal.com.

I have never seen a properly installed PSS collar move, but I have an SRC on my boat, just in case.