21 pitch

[TRAILN]

Hi,

I've got a 115 Merc 4 stroke pushing an 17.5 aluminum fishing boat. I wanted more top end speed and was thinking of a 21 pitch prop. My hesitation is the Spitfire 4 blade 21 pitch says for engines 135 hp - 300 hp.

My 17 pitch 4 blade aluminum runs 6400 rpm at 40 mph
My 19 pitch 4 blade aluminum runs 6200 rpm at 43 mph

full throttle manufacture range is between 5800 - 6400

My question is should I try a higher pitch prop even though its not technically rated for my engine size?

 

[Sea Rider]

Assume you already have it or plan buying one ? If losing + 200 revs more should be in the 6000 rpm range with a 21 pitch and probably achieving just slight more top end speed than with previous 19 pitch.

Happy Boating

 

[SkiDad]

try 19p Turning Point Hustler - that might get you a few mph. I don't think 21 is the way to go and that prop would not be the right version.

 

[TRAILN]

I like the Turning Point idea. I've heard good things about them.
They offer a 14x19 and 13x19 what is the biggest difference?
I've seen guys had to notch their trim tab to make them fit.