Please explain wiring diagram for me
Scott, normal operation would be as follows.
Port switch in position 1.
Stbd switch in position 2.
If you get into trouble and need to use the other battery to start a motor. Make sure the "Good" motor has it's switch in the off position while starting the other. Once started you can switch the "bad" motor to it's normal position, and then go ahead start the good motor in it's normal position.
At no time do you want both motors connected together and running.