I have a 1981 3007 aft cabin. I have reviewing and drawing out the starting power circuit because I am confused by the 3 batteries and how the house circuit seems to be designed. I drew this schematic/design based on the wires I followed. What led to this initiative was the fact I could start the engines no matter which position the switch was in. If it is in position 1, I start from the battery #3. If it is in position 2, I pull from the battery bank consisting of battery #1, Battery #2. I want to add a larger battery bank and install an inverter, but I need to understand the existing system to ensure I can rewire the engine batteries to work with the engines only. The new bank will become the house bank and power everything except the engines. My questions are: 1- How does the alternator output tie into the existing circuit? ( I forgot to follow the wire when at the boat the last time) If this was a domestic car, I would expect the alternator output would tie into the starting circuit and feed back to the battery on the main line. (I could be on the wrong return wire) 2- Does anyone know if this is the case? 3- Can / Should I wire the engine batteries directly to the engines, bypassing the battery selector switch and depend on the ignition circuit to isolate the power from the system? 4- Does anyone have a diagram that would be better than what is installed now? Note: The charger has 3 outputs, not 3 chargers