Alternator exciter wire issue
 

Got an 2007 Epic 23V with the Volvo 8.1L. It has two Optimas with a perko switch. They are two years old and taken care of by the book. I go out on the water with full charge from storage, we ride for a while and PP screen goes blank from low voltage. We go to load and as we're cruising the screen did come back briefly. Anyway, so I figure my alternator is shot with only about 250hrs on it. I take it in to an alternator shop, it tests fine. He tells me to test the exciter wire at the plug by the alternator, it should have the same voltage as the batteries. I did that and got 11.1V on the exciter wire and 12.2V on the batteries. I called him back and he figures that's too low of voltage drop for alternator to kick in. Anyone got any advice? How do I find/fix that voltage drop? I don't have my hands on a wiring diagram yet to even see where that wire goes. Any light on this is much appreciated.