Nissan prop help...

[Bob Gordon]

Need a little help from the guru...I have a 90 hp Nissan, 1907 year on a homemade 19" medium weight flat bottomed decked bass boat with the 90 it will only reach 4300 rpm wide open, is sluggish on the takeoff, motor is set at the proper transom height and has a Nissan aluminum prop marked H13.25X17P.
Boat feels way over propped with this prop and wide open at 4300 rpm,s will hit GPS 36 mph. If I go down on pitch how much and will dropping a inch or two to get the R,s up where they belong and will I lose any top end if the increase to factory maxium rpm,s is reached?..

I don't know the loaded weight of the boat but it's less than a glass bass boat of the same size, think decked 19' Jon boat with three batteries, trolling motor, gear etc and a 20 gal. fuel tank...snag

 

[TOHATSU GURU]

Re: Nissan prop help...

The RPM's sound wrong for the speed and what I imagine your boat must weigh. But, For every inch you move with pitch you will see a 200 RPM dofference...In theory. Going by your numbers:

Dropping down to a 15 pitch would put you up at the 4750 RPM Range and would probably drop your top speed down to 33 MPH.

I think your tach is off, the engine is sick or the boat is a water logged pig. I would try to borrow a prop from someone to try first, before buying one, as I think something else is your problem.