Mothers battery dead

boatman37

Well-Known Member
Jun 6, 2015
4,210
pittsburgh
Boat Info
2006 Crownline 250CR. 5.7 Merc BIII
Previous: 1986 Sea Ray 250 Sundancer. 260 Merc Alpha 1 Gen 1
Engines
5.7 Merc BIII
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.
 
I can't figure out how you determined that a battery is 98% charged and the other is 1% charged. What kind of device gives that intel? That aside the symptoms make me think of a bad ground connection somewhere. Those batteries need to be tested by a technician that has the proper battery testing equipment. This will turn out to be something very basic.
 
We have a battery analyzer that we use at work to test deep cycle batteries used for remote sirens and stuff.
It tells us a lot if info, including the percentage of battery strength.
They're around $5000.00 each.
No matter how many batteries are connected in the string, it will analyze each individual battery.
 
yeah. he borrowed his dock neighbors Schumacher charger (I have one too that displays charge %). Not sure how accurate they are but there is a huge difference between 98% and 1%. But yeah, I told him to take it to Auto Zone or Advanced Auto and have both batteries tested.
 

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