I have a Sony 10 disc cd/mp3 changer. It's been in the boat two years and has worked fine. Lately, when it changes to another song (only in the changer, not the head unit), I get a wierd and crazy noise coming out of the speakers. The noise is as loud as whatever the volume setting is at that time. The sound is electronical in nature, not engine noise, hissing, or popping. Any ideas???