I need advice

[debruin]

Hi guys after thinking a lot about it, I drew a basic 3 seat water scooter powered by a 60cc 10 hp engine I already have. I assume that the shaft on which the prop is mounted is supposed to be 1.5x as long as I have drawn it. And can a prop intended for a 5 hp Yamaha engine handle the 10 hp engine if I most of the time go 2/3 throttle? And what ratio should the gears be? Max rpm is 15000. If you see anything wrong on the drawing please tell me, I'd rather not build something so it can sink.