Charging issues

[Bryan Innes]

I am having an issue with the port alternator charging. If running on its own it’ll run at 13.4 volts but when I fire up the starboard engine it spikes and stays between 15.5-17 volts depending on RPM. The starboard motor never really goes over 13.4 volts. Both alternators tested good. Both engines run fine independently, it’s just when they are both fired up that I have the issue. At the end of last season is when it started doing it and it blew a battery up on my way home one day. Any suggestions?

 

[NotHerDecision]

Do you have a battery isolator? That could be the issue.

 

[Bryan Innes]

Do you have a battery isolator? That could be the issue.

Just tested the isolator. Bank 2 connection has and open on it. Bank 1 has flow. Replacing tomorrow. I’ll let you know how it goes, thanks.

 

[Bryan Innes]

Do you have a battery isolator? That could be the issue.

Thank you for the suggestion. That was exactly correct. Put new one in and both alternators were reading a steady 13.8 Volts.