Well this is the project I really didn’t want to do at this time. Mercury manual says AGM batteries. I was gonna just put 2 in and isolate the 2 banks but the wiring was horrible and all 4 batteries were group 24 start batteries. So I ripped em out and ordered 4 deka group 27’s. I’m gonna go ahead and change the charger also. The old one still works so I will keep it on the boat for a spare in a pinch. More pics to follow.