Well new here first post, here goes. Went up with to check on my boat today , (frst boat) and looks as though all my batteries are dead. Didn't have a lot of time to inspect weather they had froze and swelled although I'm assuming they have. The boat is a 1989 3207 aft cabin. It has twin 350 mercs looks like 2 start batteries and 4 220 Ah 6 volt house batteries. I left the selector off in the fall but obviously something has drained them. I'm looking to find out how these systems are supposed to be wired I can't really find any solid info. I've had the boat since August 2016. I was confused about the the 12 volt system from the start as there is a battery monitor that flashes battery voltage 4 battery's but the selector switch only has 2 and all . (Boat not equipped with a generator ) so basically I'm looking for wiring diagrams / info as well hope someone can give some advice on where to start here.