prop suggestion for Johnson 90 on 900 lb boat

[eli_lilly]

Hello,

My 1972 Merc 650 was propped at 12p and ran in the correct RPM range. I am switching to a 1989 Johnson 90 and am wondering what prop pitch (aluminum) I should start with. Some online calculators I have used suggest between 21p and 24p. I am a general purpose boater and don't care about top speed or hole shot, I'd rather be kind to the engine. The hull's dry weight is around 900lbs (1969 17' Hewes Tarpon fish/ski) , the engine weighs around 350, and I usually carry 24 gallons of fuel and ride with 300 pounds of people, with minimal weight outside of all that.

Thanks,
Jeff

 

[WillyBWright]

Re: prop suggestion for Johnson 90 on 900 lb boat

With an average planing boat where 90 is at or near the max rating, 17 for pulling, 21 for speed, 19 for average. For SS props, you can probably bump those up an inch.

 

[eli_lilly]

Re: prop suggestion for Johnson 90 on 900 lb boat


I'm going to stick with aluminum for now. I am curious, if the planing boat is rated for 140hp in what way would this potentially affect the pitch selection?

I hope that you and the others here who help all of us out realize how much of an asset you are to the boating community. I don't think they teach this stuff in schools. My first year of boating has been an absolute pleasure, I never thought I'd use the boat this much or have this much fun, and I'd have never turned RPM 1 if it wasn't for the iboats community.

-Jeff

 

[WillyBWright]

Re: prop suggestion for Johnson 90 on 900 lb boat

Aw shucks.

90 is about the smallest Hp V-4 and 140 about the largest. You might have to bump the props I suggested down 2".

Keep on Boatin.