Bill,

3000 watts is a lot of of AC power for a small to medium sized boat. Most of
the time you will be using only a fraction of the output. But, that doesn't
mean you can undersize the wires. 4/0 cable should be fine. I'm using 4/0
cable for my 4Kw inverter/charger but it's 24 volt on the DC side so the
current is half that of a 12 volt unit.

If the alternator in your outboard is indeed a 70 amp model, the 12 gauge
wire is way undersized. For the distance you listed you should use #1 AWG
for the positive and negative cables between the alternator and battery. You
should fuse the positive wire near the battery. I would suggest an 80 amp
ANL fuse and block. If you use the proper sized wire you won't need a fuse
at the alternator.

Rusty

"Wet-n-Wild Bill" wrote in message
m...
I do understand the math P=IE! Another concern is recharging the battery
bank for the Inverter. I heard that my outboards have dual 70 Amp
alternator outputs, if so i should be able to utilize the second output for
the inverter battery bank?

My wire size requirement for a 3000w inverter is 4/0 with a 450amp fuse.
The distance of the outboards to the I-Battery Bank will be about 15-20
feet. I'm not sure what the size wire for the alternator output possible
12 ga. Should i increase the size of the wire for this run?

IF i donot have a dual outputs on the alternators what other options would
i have to re-charge the batteries underway?

Bill