Re: Aluminum Corrosion on lower unit
I use a marine primer -- had been using zinc phosphate primer successfully, but I also see reference here to zinc chromate so I will be checking up a bit before the next primer purchase. Actually, I think wire brushing, priming and painting are the best protections -- but it all depends on use/exposure. If you are having a continuing problem, I would definitely install a sacrificial zinc on the ventilation/cavitation plate as well as priming and painting around it. Salt water is worse than fresh water, and leaving a boat in a marina slip is a hazzard because of the potential for galvanic corrosion (need to keep the lower unit raised out of the water).
