Galia 515 bowrider & Yamaha 90 2stroke optimal height testing.
3rd hole seems to be the best with original 17" aluminium prop, but 4rd hole is also strong alternative but only with steel prop.

Btw. when it comes to rpms, i have a doubt about my tachometer: 17" Ballistic prop + 5100 rpm + 34,8 knots + gear ratio 13:26 = only 2,5% calculative slip ... ?
http://continuouswave.com/cgibin/pro...
I quess the real rpms are appr. 5300 5400.

A good dialog about engine height (with steel props):
http://www.veradoclub.com/smf/index.p...

I think my boat won't go faster than 35 knots with 90hp. I need more horsepower (boat maximum is 150 hp) or lighter boat ;) On the other hand, with normal cruising speed (28knots) Yamaha 90 hp is pretty quiet and economical.