Prop Pitch for 1990 90hp Force

[Illini River]

Hi all,

I'm wondering if I should go to a lower pitch for my motor. Right now I have a 16 pitch prop and I get about 4000 - 4200 RPMs at about 30-33 MPH depending on load. I think the original prop for this motor was a 15 pitch and I'm thinking about taking it down to get a few more RPM's/MPH.

Thanks!