So, on the Harley motor, what horsepower at what rpm? Water cooled?
Cross those figures with SeaDoo, Yamaha, And Kawasaki jet pumps.
Just so ya know, bolting an engine to a pump is like strapping it to a dyno, and then going to lunch, with it wide open. Will it still be running in an hour?
Others have put pwc power trains in mini hulls, with great results.
Good luck,
Dan'l