1978 Johnson 85 hp. What would changing a prop from a 17 to 19 pitch

[enduro155]

What would this do for top end speed. The boat is a fibreglass vanguard Calais. It's 16.5 feet long not sure of weight though.

 

[Artwerke]

Re: 1978 Johnson 85 hp. What would changing a prop from a 17 to 19 pitch

I have a 17.5 ft Bass boat with an 82 90 Rude on it & it pulls a 19'' SST fine, even pop up with a tube in tow.

 

[jestor68]

Re: 1978 Johnson 85 hp. What would changing a prop from a 17 to 19 pitch

Here's a generalized answer to a general question.

Provided the motor can still operate within it's recommended rpm range, going up in pitch should result in a speed increase.

Without knowing what rpm/speed it presently gets with a 17 pitch, there's no way to know if it can even pull a 19 pitch.

Just because Johnny's similar boat does this or that doesn't mean you boat will.

 

[enduro155]

Re: 1978 Johnson 85 hp. What would changing a prop from a 17 to 19 pitch

This boat was in my family for a long time. And my pops had a 19 and 17 pitch prop. The boat goes about 38mph with my wife and 2 small kids. Not sure on rpm. But the motor has to be rated for it as he was a mechanic and wouldn't of had it on the motoe if it wasn't recommended.

 

[Fleetwin]

Re: 1978 Johnson 85 hp. What would changing a prop from a 17 to 19 pitch

Without knowing RPM's you're guessing.

 

[jimmbo]

Re: 1978 Johnson 85 hp. What would changing a prop from a 17 to 19 pitch

Top speed with be within 1/2 mph of the other prop along with approx 400 rpm drop and slower holeshot.