Gday mate Darryl here from Australia I do have yamaha 90 2stroke also.Can you tell me carbi Fuel /air screw turns,timing degrees at idle and WOT,prop size and fins and number,size and weight of boat,fuel used any additives,etc as I would love to improve performance as good as you cheers
Stock fuel/air and timing,, 4.95 meter long boat, 500 kilo. Fuel 95 ron. Triboron fuel additive, 50 milliliter aceton in 30 liter fuel. 4 blade original Yamaha 13 1/4 X 18 prop for low rpm cruise speed,, engine mounted as high that is possible on the boat ,, No jack plate,,( A hydralic jack can be installed to lift the Yamaha even more.) www.boats.net/parts/detail/props/Y-MAR-GYT4B-V4-18.html www.boats.net/parts/detail/props/Y-MAR-GYT4B-V4-18.html
+Jerry Chan Performance 4-Blade SSTP Typ K 13 -1/4x18 Yamaha original so 18 pitch. The prop that came originally with the Yamaha 90hp 2 stroke was a aluminum white 3 blade 17 pitch.
3 blade stainless steel = more top end speed. I used this 4 blade propeller to get lower rpm cruise speed ,, 19 knots @ low 2700 rpm ,,, ,,,17 knots @ 2600 The boat would not even get on plane @ 2700 rpm whith a 3 blade prop. : )
my 90 on my 16 wellcraft does 27 kn at only 2800 rpm so theres something not quite right with youre equation and the lowest plane speed for mine is 1900 rpms at 17 kn
