I put some Ground Loop Isolator RCA cables from the deck to the amp and the problem was gone. My 2008 XLV came from the factory this way too, which I feel is unacceptable on a 55k boat when the fix is either moving the grounds (ground all amps and deck to the same spot) or some simple RCA's. An easy fix, but not one the owner should have to make.

http://www.thesource.ca/estore/produ...roduct=2700054