I disconnected my boat's starting/cranking battery and when I went to put the new battery in I realized that there was a 3rd wire that seems to come from toward the front of the boat.
I connected the 2 wires from the motor, red and black, and it worked. So I don't know where this 3rd wire (black) is from (left disconnected).
Is it from the boat's battery gauge, and if it is, does it go on the positive or negative terminal?
I know it's not for a charger as I have that disconnected.