I've kind of thought like MC, with a glass boat I don't have a connection to the wire of any kind, plus with Cannons the cable is isolated from the boat being the riggers are made of plastic. However, I know that you can get a voltage charge from two dissimilar metals in water, especially salt water. The first battery invented was exactly that. So, the only exposed metal I have is zinc anodes, and the inside of my outdrive since the outside is painted. Now, I could really see this in an aluminum boat where everything is connected in some way be metal and easy for a ground loop to exist and hold a charge, or even generate a charge.

So, is the problem more with aluminum boats or glass? If I have no current, I may actually need one to actract fish!