I agree with blaise's idea of using the boat motor and belting a generator to it (and anything else like AC compressor, reefer compressor, emergency water pump..... ) Then convert whatever the generator produces to 60 Hz 110 volt AC with electronics. This gets rid of one entire engine and puts everything in one space that is already devoted to high noise/high heat type equipment.
If you subscribe to the "produce as you consume" concept you can fire up the engine around dinner time, cook you meal on an electric stove, heat your hot water for a shower later, cool down the cabin for the night, draw down the holding plates in the reefer/freezer and charge the batts all for a quart of diesel!!