Normally... the numbers on the switches denote the batteries... not the motors. So #1 is one battery. #2 is the other battery. If your switches are wired like mine... you would want to run one switch on #1 while starting and running and the other switch on #2 while starting and running. Then,,, if you are moored and want to keep one battery fresh... just switch one of the battery switches to the "off" position.Then you can reverse the switches to start the motors. But.... you have to make sure both systems are isolated... if they are not... then power will trickle over to the other side and both batteries will go dead... There is a simple way to determine if they are not cross wired... but it would be way too hard to explain in text.

Here is a link to a cool set up for twin engine, 2 battery systems. 1 battery is always used for cranking both engines, the other is for electrical systems. Can still use both for starting if needed.

http://www.marinemechanic.com/new-images/d-bat-fig2.gif

That site also has some other pretty interesting articles on general boat maintenance.

On my boat(twin engine, twin battery, twin charging), It says to run the boat with both switches on "1". It says on the panel not to run the boat with the switches in the "Both" position or it will damage the charging system. I haven't traced it out, but I'm assuming that the"1" position on each switch runs that corresponding battery....confused yet?

Craig

Uhhmm... set switch to battery 1, put vhm (volt meter) negative on battery one negative, positive on battery 2's positive. If you show anything, you've got circuits crossed somewhere.