Originally Posted by djmarchand
Do you have a separate engine
starting battery? Do you have an inverter hooked up to the house batteries?
These are the only really high amp loads on a boat. If you have a separate starting battery and no inverter, then your highest load/supply device will be your alternator
which is typically 80-100 amps.
#6 wire can safely carry 120 amps and will work as there is no supply or load that will exceed that. You will need a 100 amp fuse at each end of the 12' run to be safe.
Voltage drop is usually the deciding factor in boat systems.
Aswg 6 or 16mm squared is much too small for this application. The voltage drop at 100 A is 1.6 v. The current
will not be 100A, but that voltage drop is way too high.
50 mm squared would be my choice, but you could get away with 35mm with some compromises.