If the 41 series Lehner or 4225 scorpion is worth a flip then their editors will drop them in the calculators and telll you the expected performance with an actual boat propeller!
FE CALC
Showds In a performance hydro with 10s lipo @ 9800 mah and a castle 240. Prop wizard selected an ABC 1918 as the most efficient prop for the setup. Resultant: 28,221 rpm 141 amps 4,955.78 watts Pin 4,728.58 watts Pout run time 4.15 minutes est speed 79.20 mph or 127.46 Km/h Eff. 95.42%