Chuck,

The copper wire I was referring to is entirely unrelated to the
fish. What I was doing is comparing the reading I would get from
connecting the zinc fish to boat ground vs. connecting a bare (at the
tip) copper wire in the water to boat ground. (in both cases with my
meter inbetween measuring current). My expectation is that by looking
at a change in voltage and current, I could learn something about
what's going on. E.g. while I do measure a current with the fish,
maybe the fish is inducing it. Now that I have the readings ... don't
know how to interpret.

My keel is iron and ideally has a succesful barrier coat of paint
between it and the salt water, as I know the keel is connected to my
boats grounding system (lightening protection). I also have a rudder
that I don't believe is tied into ground, but I am not sure. So is two
or three points under my boat creating a battery ... is the only two
points between the prop and my fish ?

Dan