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Alternator or Battery

dhyams

Regular Contributor
"Boat dead on the water yester

"Boat dead on the water yesterday due to a dead battery. It was just weird; one moment we were buzzing around on the water having a great time, and I cut off the engine to load the folks who had just finished tubing. When I tried to crank again, nothing. Luckily, a friend of mine was on the water as well, and the boat ran fine with his battery.

So how do I tell whether it is the battery or alternator at fault? I've replaced the battery already (it was 3.5 yrs old) and the boat will crank fine, I'm sure. But, I don't want to be out there again and have the battery go dead on me again."
 
Watch your volt meter on your

Watch your volt meter on your dash. 13 to 15 volts at ~ 2000 rpm then all is good for the alternator. With the key in the on position and NO motor running the meter should read ~ 12 1/2 volts.

If you have a dvm digital volt meter measuer the battery with no load on it. it should read 12.6 volts fully chargered. that is 2.2 vdc per cell.

If it reads 10 -11 volts then you have a dead cell. Very common problem with marine batteries...........

If you have a dvm with the motor running put the leads across the battery terminals and rev the engine to 2000 rpm and check the voltage. Again it should be between 13 and 15 volts DC. If it is then chaging system is working correctly.
 
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