To me, this is a bit confusing??

Does your boat have an inboard engine with a propellor shaft?? or are you
talking about an Outboard motor or Out drive??

A properly installed marine engine will have the thrust bearing in the
reduction/reverse gear. If it is an OB or Out Drive, the thrust bearing is
inside the lower unit. I've never heard of a thrust bearing at the
propellor. There should only be a water lubricated cutlass bearing.

Please provide more information on what you have, engine/rev. gear, etc. and
maybe we can figure a solution.

Steve
s/v Good Intentions