The skyboat will have an electrical motor for propulsion. Current favorite is the AC Propulsion motor. It's got 200 horsepower max, and only weighs a hundred pounds, wow!

After further thought and calculations it is understood that the propulsion system of an UltraLight SkyBoat must weigh less than 50 pounds. That means the generator should weigh half as much as the two electric motors. The generac 800 parts weigh; 7.4 for case with integral gasoline tank, 3.5 for inverter, 18.5 for the 4-stroke, 39 cc engine. That is a total of 29.4 pounds. [!] The external case has gotta go and hopefully the blower shroud will hold the noise level down. That'll give the Personal UltraLight Dirigible, PUD, a 22-pound, one-horse power plant.

Dsci4008EngineSmaller.jpg
Generac 800 uncovered.

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Hi from an anonymous but not coward just too lazy to sign up.
TheOneLaw

If using a propeller,
Your propulsion power requirements are directly related to airflow (V*dM)
so you can get away with a vastly reduced motor size with a bigger prop.
(I learned that the hard way, somewhat, building over 30 props by hand)
Think about the dudes who achieved the human-powered helicopter,
nominally 600w but that was _lift_

good luck, see you up there someday...