Could boat be throwing voltage into water?

[slickwater]

I got a new graph last year and I think that we are not catching as many fish as we did before we got the new one.It just seams that i get a report on where to catch salmon and we go there mark all kinds of fish and don't get bit maybe 1 or 2 hits all afternoon. I know there are other boats catching fish in the same area.What is a good way to test this?Without shutting off the graph.

[Priority1]

Check this out.

http://www.scotty.com/scotty-support/documents/BBox%20Booklet%202003.pdf

[slickwater]

Check this out.

http://www.scotty.com/scotty-support/documents/BBox%20Booklet%202003.pdf

Thank you for this.

[slickwater]

I just talked to my boat Mechanic and he says i should try and get this mercathode kit.But he is not sure about it for fishing. There is anodes on the boat and lower unit already.My boat is a 1995 221 Starcraft Islander I/O.Does anyone have any suggestions about this.