Hunter 34 with an odd battery setup.
As you can see someone messed up the battery wiring, didn't even use the right colors.
Any guesses as to what the PO was thinking.
As you can see from my crude drawing a negative wire from the battery is going through the bulkhead and one battery's negative terminal is not even attached to anything.
Any guess as to what the idea was.
I'm guessing that the two red positives go the switch. the negative goes back to a negative bus bar or alternator. On the other side of the switch where I can't see is a red wire to the positive switch panel I suspect.
I'm assuming that it was originally a two battery setup and someone added the third battery and never finished the install.
My PO phased some cables, apparently he had a lot of Black lead. I don't condone it but properly marked it's OK if you understand it. Your diagram is good without the positive from the third Battery connected to the second, you loose isolation that's what the main switch is for. Make sure the other end is taped as well, phasing wires is done a lot but only works if maintained on BOTH ends of the cable, but still not the best way..