What is Minimum Diameter for a Propeller Shaft

[4HMainer]

Originally Posted by foolishsailor

Regarding what has changed...there was a middle phenolic bearing that had been in there that had over time had melted and seized onto the shaft and prevented and water from coming up to the inner cutlass bearing. This is another reason I am looking to put in a larger diameter stern tube so that if I decide to put back the middle bearing then I could have the machinist cut larger water grooves...

Sorry, but phenolic bearings don't melt they harden with heat and then polish, at failure they turn to carbon! if you mean a rubber bearing in a phenolic carrier that is something completely different. Phenolic bearings are chosen in place of other materials because they don't melt.

I'm not surprised a centre bearing in the tube got warm, did you have a good water feed? was the feed direct from sea water or after the engine (which could be too warm)

I'd go for a good water feed (direct from sea) and a couple of maritex bearings a bit longer than the normal 4 x shaft. mounted in epoxy so that they can be easily removed when they need changing, but you should get at least 3 or 4 times tha life of any rubber bearing and the shaft will move less.