Yep, I got several VOM. After being told disconnecting one leg could do more harm than good, I found the owner's manual online. It is a Promatic 50-3 from Pro Marine. It states that if you only use two legs, connect the third leg to one of the two legs being used.
So, with the Genny leg (I thought, read on) disconnected, I took my meter and checked the voltage at each of the three post on the charger (Charger is OFF). The thinking is if one leg is not connected to a battery it would read 0Vdc. To my surprise, I had 12Vdc on each leg.
I went back to the genny and tested the diconnected leads. Yep 12Vdc. I connected them back up to the battery for now.
I do know the PO added a third battery in the engine room. My guess is he took the geeny leads from the charger and conected it to this new battery, then ran from that battery to the genny battery. I will have to confirm this.
For now, when I check the charger when first turned on, the red light comes on and charges at 14Vdc for a brief period. Then the green light comes on indicating a floating stage and is at 13.3Vdc.
Once I get all the wiring figured out, I will have to keep an eye on water levels, not run the charger 24/7, only when I am on the boat and I see a new charger in my future....