I have a 92 Blue Fin Spectrum 1750 with a 3.0 mercruiser alpha one stern drive. WOT I get just under 33 mph @ 5000 rpm with 32 gal fuel, 2 people and a Boxer on board according to my fish finder. I want to get some more top end speed, I currently have a 15x17 aluminium 3 blade. Would I get much of an increase going to a 19 or 21 or am I better off staying with what I have? Thanks for any help