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]

Source of the post 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.