So mother and step-father have a pontoon boat. Over the winter he had a local marina install a Perko switch and 2nd battery. A couple of times this year their battery was dead. I knew they had a 2nd battery but didn't know about the switch until today. So my mother calls me and says boat won't start and both batteries are dead. I ride down and see the switch set to #1. Turn the key and nothing. No click, no power trim, nothing. He has a battery charger connected so I turn the switch to #2 and it fires right up. Asked him if he had tried that and he said he did not. Well after about 20 seconds it stalls out and now nothing. No click, nothing, on either battery or any switch position. Depth finder and horn work. We removed the original battery that came with the boat (no idea how old it is) and check the newer battery and it's at 98% charge. Check the old battery that we removed and it's at 1% charged. Tried starting it again with just the newer battery on all switch positions and nothing still.
I told him to go get both batteries tested. I'm pretty sure it is either a bad battery or maybe a bad Perko switch but doubt that is it. We were limited with our tools so I couldn't check anything for continuity.