Using David Gerr's widely accepted nomograms you propably are spinning

Thank you Bob, I did forget to mention the gear ratio of 2-1 My goal is to operate at the high end of the displacement range 8 to 9 knots but wanting to make sure that the engine can reach its rated RPM at full throttle. Full throttle RPM for this engine is 2500 Cruise should be 1800 for 9 knots, I'm estimating. Does the 30 x 22 wheel seem to be correct? Hal Oakes Traveler, Albin 43 Tenants Harbor, Maine > Hal, > You really need to tell the list what the gear ratio of the tranny is! > Also I think anyone would be very reluctant to make a recommendation without > seeing what the WOT RPM and cruise RPM would be. You do not have enough > horse power to operate at more than semi displacement speeds--ie probably 12 > knots to 14 knots will be the top. You will probably cruise at 10 knots max > (based on my experience in similar size boats with about this HP). To get > the boat on plane would take 700 to 800 hp.. > > Using David Gerr's widely accepted nomograms you propably are spinning > the shaft at 1200 RPM--and have a 2:1 ratio--and the speed that you are > getting is about what is predicted. > > Bob Austin > >