Yamaha90 optimal height?

Galia 515 bowrider & Yamaha 90 2-stroke 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 ... ? I quess the real rpms are appr. 5300 - 5400. A good dialog about engine height (with steel props): http://