Just a wild guess here, but what type battery are you running? Standard batteries really take a beating in a boat, and could shake loose inside and cause the charging system to go nuts and spike the current to the moon until the short in the battery burns itself apart.......Just a guess, and how much is the "surge protector" that the MSD guy asked about........This is by no means an attempt to talk you out of the Mag idea, they work great, and should last a long, long time in a boat........MP