HUH?????? Sorry to inform you, but electolysis IS corrosion bud......

Harley, if the only zinc you have is on the motor, that is definetely a (maybe THE) problem. You should have at least one on the hull. You can buy different sizes, bigger the better, that bolt on. I do not think they even make one that "welds" on, since zinc and aluminum would not be compatable for welding.
Get a handle on it now, especially if you are going to do more salt fishing, as once the corrosion (electolysis) starts it can take off really fast..... Get that electrode on your hull man!

MC