I bought a Zenith at Home Depot, which I place in front of my forward hatch blowing into a cowling I made from 1/4" plywood. 8 tons for 150 bucks, start up at 8 amps. Be sure to hang it so the water
runs out of the AC drain hole (and boat) instead of into the V berth.
The parameters are that it was the lowest start up amperage (about 8) and cheap
because a season in salt
will probably kill it. Using 12V fans in cabins to circulate air, I have survived heat to the upper 90's all summer with a cool interior
The amperage is very important because a 30 amp circuit does not leave a lot of wiggle room for keeping the ice box and other equipment
(like your 10 amp saw) from topping out beyond the circuit breaker load. Many window units start up at 12-15 amps, enough to trip the breaker when other things start simultaneously or if you just have a decent load running.