Re: Too hot to sail...
I've ran these equations many times. Using your auxiliary to power AC for the boat is real doable. You can outfit the engine with junk yard parts (dual pulleys, brackets, compressor and even evaporator and fan) enough that the only thing left is a small wat heat exchanger for the condenser.
Make sure you grab a system that uses R-430 NOT R-12/22. This avoids you needing a "refrigerant recovery permit" and keeps the EPA off your ass.
The thing to remember is that your engine has been used to power land vehicles. There is no such thing as a MARINE ONLY engine of only 12-160 HP. The brackets are there on ebay for the cheap taking and the compressor, evaporator and fan as well. Just find the engine and inquire. If the seller has the auto, boat whatever and is stripping it they will be tickled as hell to find a buyer for those things that would go to the scrap dealer. the only thing there is that the pulleys they may want more for to part with, however whoever is buying the engine for replacement of another will certainly have what they need as per that and thus will never miss them.