There are actually some products made for repairing shafting. Shipyards use this stuff often, as a new shaft costs a huge sum...
For fixing cutlass bearings into ovaled out shaft struts, ITW makes Chockfast Orange.
For grooved and worn shafts, look at Phillybond. It depends on the kind of wear, but most of the time I see where the shaft has worn undersized, folks have a machine shop turn grooves into the shaft and then over fill the grooves. When you haul out
and see the grooves it is time to re-do the job.
I would spend the money
and have a machine shop magnaflux the shaft and make sure you don't have any crevice corrosion
and cracking that the naked eye can't see. Stainless is funny
, in that you can have a pit on the surface and the inside of the shaft is made of swiss cheese and looks like metal eating termites have gotten inside.
ITW Chockfast Marine | Industrial Grouts, Adhesives, Repair Products and Coatings