Hey, guys, this will only be used to go cool off for 10 min or so while making a drink. Or when cruising and to use shore power while at slip. It's a small compact 7k BtU, 900 watt portable a/c unit mounted in cabin with exhaust hose that comes out a vent by passengers knees.
The inverter is a 2000 watt continuous and 3000w surge. It a Tripp Lite inverter that also doubles as a charger with shore power at dock.
Again, this a/c will only be use while at slip and short periods while out on water. thx.

oh, and i have 4 blue top optima batteries. could prob run for 1.5-2 hrs if i really wanted to.

I had a Heart Interface inverter which also charged the batteries when it was plugged into 110. I mounted in under the back seat as extending the cables to the batteries is not recommended. I used a 10 gauge extension cord to run the power to the sink area. As others have mentioned even with 3 type 24 deep cycle batteries the power doesn't last forever. It was better running the microwave and coffee pot when the motors were running to supplement power. A high amp alternator would be a plus, one that had high output at idle.

What size of inverter are you using?

You can mount it anywhere. Just gotta size your DC side cables to avoid voltage drop.