Red wire on back of alternator

[Helmsman]

I was checking fluid levels, etc. the other day and found a wire (red) laying unattached at the back of the alternator. I checked the other engine (2006 Crusader 6.0 liter ... carver 33 SS) and the wire was attached to a post screw on the back of the alternator. So, I attached the other one while I was in there. I can't find anything describing what it is so thought I would ask here. It appears to run to the isolator and then on to the battery so I am assuming it charges the starting battery?

Any help would be appreciated.

[Viper]

Sounds like they've incorporated an isolator into the charging system to charge two or more banks while keeping them isolated from each other. If it was disconnected, I suspect it either came loose, or intentionally removed likely due to a failed isolator or other charging related issue. Does the other alternator go to the same isolator?

If you know how to use a multi-meter, it's an easy test to check the isolator for a failure.

[Helmsman]

Qr Bbpost Sounds like they've incorporated an isolator into the charging system to charge two or more banks while keeping them isolated from each other. If it was disconnected, I suspect it either came loose, or intentionally removed likely due to a failed isolator or other charging related issue. Does the other alternator go to the same isolator?

If you know how to use a multi-meter, it's an easy test to check the isolator for a failure.

I can use a multimeter somewhat. Can you let me know what I need to do?

The previous guy had the isolator replaced because it failed. It was done at a reputable boat yard by their most highly thought of mechanic.