I need some electrical expert diagnosis help. I'm having two issues, the stereo buzzes when the motor is running (fine when it's not running) and we noticed on Friday after a couple hours out that the volt meter on the dash read below 13 - much below: 8-10. Returning to the dock at the end of the day at speed and probably 3-4,000 RPM, the volt meter read 8. I think the two issues are related.
The week before, when we were pumping the sacks full, the stereo was on with the engine running. When we plugged one of the pumps into the lighter on the dash, the buzz began. I looked over the circuit breakers, the amp fuses, etc. and everything was fine. The buzz over the stereo has continued every time the engine is on. Reading up on WW, this has normally been a ground problem. But after looking over the stereo & elec. system, I'm at a loss for what else to look for.
I thought the buzz & volt meter might be related. Via a hand-held meter, I checked the volts at the batteries with engine running - it read 12.6. I also checked at the alternator - it read 13.2 at idle and 14 at 2,000 RMP. So, my alternator is fine. And, I'm pretty sure the alternator hookup to the batteries are fine.
So, I'm thinking somewhere up near the dash is some sort of short drawing down power that shows on the on-dash voltmeter. When testing today, it read 11-12 instead of the 13-14 it should.
By the way, just this week (before all the testing today) the boat has two brand new deep cycle batteries, each testing 12.6, engine is stopped.
Are the problems related? What do I look for next?