Just bought a 1997 Maxum 23SC with a 5.7 merc. There are three batteries on the boat with one single power 50amp. alternator. Two of the batteries are in<br />parallel for an inverter and stereo amp. and one for starting. It is wired with one orange wire coming from the alternator to the starting battery and another black wire coming from the alternator to one of the batteries in parallel and the batteries in parallel have a negative wire going to the starting battery. The starting battery has a ground to the engine block. <br />The question is are the batteries in parallel isolated from the starting battery or when the engine is off can the batteries in parallel dump back through the alternator into the starting<br />battery or the starting into the batteries in parallel.
