Is there a way to test all of a boats electrical system without the motors installed? While the motors are out, I want to test the bilge pumps, trim motors, blowers, lights, etc. If I hook up the battery, does the engine harness have to be powered and grounded to complete the circuit? I tried hooking up the batteries and left the starter cable (red) and block ground (black) hanging loose. I was unable to power anthing up. Next I tried hooking up alligator clips to the engine harness pins (red) and (black). No success. I did notice that the port engine harness has 3 large wires (red, black, and orange), while the starboard engine only has the red and black. Do I need to hook up both batteries, and if so, what is the large orange wire used for. Also, there are 2 battery switches labeled 1, 2, Both, and Off.

Thanks.
Doug