Voltage Problem

I will start this by saying I struggle with solving electrical issues.

I went out yesterday and when I started the boat each time, it sounded like I did not have a lot of power coming from the battery. It would be just enough to turn it over. At one point there was not enough juice to turn it over so I switched to the other battery. It also acted like it was low. When I got home I put the charger on it and it showed both batteries full. I tested with a multimeter and both checked at 12.5+.

I cleaned the battery and engine ground connections

When I check the voltage at the ignition switch it is it is 12.5, but when I turn to the key to the first position it reads 11.5.

I tested the volts from the starter to the ground 12v

Tested from positive on battery to engine ground 12v

Tested the voltage at the fuse box from Pos to neg and it was 12.5,

When I test the voltage from the battery positive to the hot wire on the ignition switch in the on position I get 1 volt (was hoping for 0), if I turn on the bilge I get almost a 2 volt reading..

Not sure where the problem is or how to pinpoint it, but suggestions sure would be appreciated.
Tom

I have deep cycle batteries (which what came with the boat with 690 cranking amps an 101 amps/hour

Testing voltage from positive at starter to ground on engine it was 12.5 then when cracking it dropped 11.9 volts.

Orlando76 wrote: Oh boy you're gonna get reamed about the deep cycle. That's like asking which tube performs better. I myself feel the stock 351 is fine with it but everybody disagrees. Mainly your batteries won't last long with a deep cycle.

Yep expecting that.    

Tom,
The .6 voltage drop is not bad at the starter. Considering your batteries are rated in amp hours as well as cranking amps and the low drop, I'd have to say they are combination starting and deep which is a compromise between the two. There's also a chance that the starter isn't pulling the amps, then you will not see a big voltage drop so, I'd look at the starter is self. Personally I'd open it up and check the brushes and the commutator. If the brushes look short replace them and then clean up the commutator. I wish there was an easy way to get amp draw on a starter but it involves a shunt or current doughnut and meter that most don't have.

Won't take a charge, barely turning the engine over... Time for a new battery. Don't buy a deep cycle. :)

TRBenj wrote: Won't take a charge, barely turning the engine over... Time for a new battery. Don't buy a deep cycle. :)

Unless stated voltage drop is incorrect, it's saying no but a load test on the batteries is not a bad idea.

My guess is a bad Perko switch. I see it all the time and seldom does anybody ever consider it a possibility. I have seen starters and batteries and even cylinder heads pulled for a bad Perko switch, Easy trouble shooting is load test the batteries, Fine? Ok now put the tester on the battery connections at the starter. Low? Put the tester on the switch terminals and you can now load test in and out of the switch.

baitkiller wrote: My guess is a bad Perko switch. I see it all the time and seldom does anybody ever consider it a possibility. I have seen starters and batteries and even cylinder heads pulled for a bad Perko switch, Easy trouble shooting is load test the batteries, Fine? Ok now put the tester on the battery connections at the starter. Low? Put the tester on the switch terminals and you can now load test in and out of the switch.

He's already done that. Please read again. No voltage drop so it's not whatever switch he has for the two batteries.

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