Hi Dale: Sounds really strange. Are you sure the holes are through the hull and not just the paint? Are there any dissimilar metals in the area for through-hull fittings? Assuming it is not paint my suggestion would be to find a surveyor with an audio gauging system, and then check the hull everywhere for thickness. If you find problems, you might want to take a few samples of the hull and send them off to a lab for analysis of the alloy. Also, check your electrical system to be sure that: Shore power comes aboard via an insolation transformer and the shore system ground is thereby isolated from the ships ground. That the negative side of the DC system is isolated as well as the positive. If the negative side is not isolated, it should be hard wired to the hull (i.e. you don’t want an intermittent ground to the hull). Be sure that there is no positive leakage. Even tiny amounts will cause havoc with electrolysis. Let us know what you find and good luck.–Steve Dashew