If you only need 35 hp, honestly, I'd get an air cooled VW motor. It will run as long as there is gas in it, most come with a generator instead of alternator (sucks for a car, great for a simple stationary motor), they sip barely any fuel (single carb with a 28mm venturi) and are air cooled so no radiator or hoses to worry about. Plus you can get one cheap.