Low Voltage on Meter

rmrstlmo

Was able to get out on the water over the weekend, finally!  Had an issue with the windlass being complete dead.  Found that the wire coming off the negative side of the battery had a bad connector.  I was hoping that would fix the low voltage issue also, but it didn't.

Last year when I stopped boating my port battery meter showed about 12 volts when engine was idling and would go up to about 13 when running at higher RPM.  This year it shows a little less than 12 while idling and never gets much better with increased RPM's.  I'm guessing I need to check the alternator. How do I do that without removing it?  Any other things I should check?

Thanks for you help!
340 FV 5.7 Merc

212rowboat

if your engine is MPI/EFI and computer controlled, your best most accurate measurement will always come from the PCM for most every reading you see on your dash... consult it and determine if it's your gauge... if you have two gauges, swap them and see if the reading follows... check connections on alternator (they surely like to corrode, but not as bad as battery posts do)..

Black_Diamond

Start with the battery. A 12v battery in reality is ~13.5v. So if it is reading 12v it is undercharged. A battery that is worn out, internally shorted or has corroded connections would be the place to start. Ideally you have the battery load tested.

rmrstlmo

The batteries are exactly one year old. Sounds like corrosion in the wires/connections are good place to start.

JohnnyCake

youstolemybeer

go behind the dash, and clean the connections to the ignition switch. It seems that the manufactures (all of them) get the voltage for the gauges from there.