I have copper lines for aft tank-to-manifold and port gen running in the port stuffing box area, and they had what appeared to be heavy corrosion. As I'm currently in the yard it seemed like a good time to attack this problem.
A little cleaning, and as other have said it turned out to be a non problem, but I will get some paint on them while they're clean.
Four hauls ago I had all the (small, cosmetic) blisters dealt with, all I found this time were two the size of a quarter. Not bad for ten years. My diver - Star Marine in san Diego - deserves the Gold Star. The boat looked like it was just painted on haul out, incredibly clean.