Guest Battery Isolator install

I recently rewired my boat and purchased a battery isolator to charge the two batteries. The instructions that came with the isolator call for me to connect the wire from the alternator to the isolator. The problem is that I don't know which wire comes from the alternator. Can someone tell me how I know which is the wire is coming from the alternator on a 2004 150? Is there a wiring diagram available?

Thanks.

[boats.net]

The green wires coming from under flywheel are the alternator wires to regulator, the red wire at starter solenoid is charge output lead. You need to double check to see what wire you need.

Thanks for the info. I am almost sure it is the charging lead that is called for but will double check.

Do you know what gauge of wire I should use to connect the isolator to the charging lead?