BS from the installer. If the system had weak batteries the amplifiers are designed to shut off so they do not damage the speakers. Any good installer would know that. It is feedback from a poor wiring job and not placing them in the right location garuanteed!

Talk about bad Karma,as we were taking the boat back to the owner's boathouse,one of the 496 rods decided to separate itself from one of the pistons,leaving the bilge full of oil and coolant.We couldn't hear the stereo noise over the sound of a rod knocking As we wait for a new warranty long block from Merc,the stereo guy will have plenty of time to fix the stereo.Sometimes I wish I had a son so I could forbid him to go into the boat business

When checking amplifier voltage drop issues, test voltage at the amplifier not the battery. Also test the ground difference at the amp and at the battery. This easy test will answer most power questions. An ungrounded amp can pull ground off the radio thru the RCA cables and obviously cause problems.

RCA Patch cables often cause this. I have even seen high quality patch cables that were not soldered properly. I used Monster Cables in the Cigarette. No noise issues. Hopefully this will help. Make sure the grounds are tight and that the ground wires are at least the same gauge or larger then the power. Power should not run near the RCA cables.