I faired mine with epoxy (International Watertite) after some sanding (and grinding out the pitting). Then painted it with aluminium etch primer and propeller antifouling (Velox Plus), same as the prop and saildrive. Works pretty well and not noticed any further corrosion. The surface where it is in touch with the bearing toroid is greased (but not the roller bearings themselves). This keeps water away from the metal just like the paint does. When hauling out, I freshen up the Velox after a light sanding.
You can buy a plastic bearing housing from Jefa, but the replacement is difficult as the old is glassed in over the entire outer surface of the housing and would be a real bastard to remove (probably have to cut it out in pieces), so not doing that while the old one is doing okay.
