Battery 1 Not Charging

alger34

Hey guy's, I have an 07 250 Fiesta Vee with 350 merc.  My number 1 battery does not charge on the alternator, charges fine on shore power, (both batteries brand new this year) but my number 2 battery shows almost 14 volts on dash and charges fine, (ran my boat all weekend).  I removed battery terminal and cleaned it up with no luck.  There is a melted cap on what appears to be the voltage regulator maybe?  It has 3 red caps and is mounted on the firewall forward of the engine.  Is this most likely my issue?  Thanks.

JC290

Sounds right a pic would help

alger34

I wish I had taken one, my boat is 4 1/2 hours away at marina.  Thanks, I will check out some parts diagrams

Cableguy Greg

The thing that you are calling a voltage regulator is actually an isolator. The output from the alternator goes to the isolator. The isolator sends voltage to both batteries keeping them separate from each other so they won't discharge each other. The melted cap has me thinking that the isolator went bad.

Michael T

I don't know if Mercury has built-in the safety for this on your engine but "back in the day" a boat owner could damage their alternator diodes if they switched their battery selector switch around while the engine was running. This would set-up what we called a transient alternator spike and would blow-out some of the diodes resulting in lowered or eliminated charging from the alternator. It sounds to me as if your diodes have been damaged.

alger34

Thanks for the info, It will definitely help me troubleshooting the problem.