I have a nitro fish and ski with an outboard motor. I replaced the stereo with a cd player and after turning the volume up over medium the head unit cuts off and on. Not enough voltage coming from the battery that is cranking the boat and running everything else. I have not put it on the water yet to see what it will do when the motor is running. I have and extra battery that was being used by the trolling motor, but I currently don't have a trolling motor. Should I use that battery separate or change my boat to a 2 battery system? I just want to be able to shut my motor off while on the water and listen to the radio for an hour or so.