How To Jumpstart A Boat With Two Batteries. Salt water fishing boats are notorious for having some sort of electrical drain that can gradually weaken or kill even the strongest 12-volt battery. Check out the picture I attached.
2015 621 starting battery will not take a charge with the on board charger and in fact no lights will light up at all on that bank. See the BOTH setting on the switch. Answer 1 of 2.
Or do you mean connect a car battery in parallel with a marine battery and thereby put some charge on the marine batt.
Luckily the trolling batteries were charged enough so I could troll back to the launch. You would not want to. The left diagram is batteries wired in series. I also have my boat at the dealer for the same problem.
