the right prop

T

tsport

Seaman Apprentice
Joined
Apr 7, 2012
Messages
31
ok i think i have all the info the boat is a 1986 gradywhite tournament bowrider it wieghs around 25-2900 lbs loaded it has a merc 3.7 170hp alpha one 1.84 drive it has a michigan wheel 15x17pitch prop on it now the boat runs good i don't have any mph info the rpm is around 4500 wot and i'm looking for a little more top end so i guess my question is could i use a prop with more pitch say a 15x 19
 
S

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: the right prop

See if you can borrow a gps for speed.Some cells have a gps app.
A 19 inch pitch will lower your rpm 300 to 400 Likely no gain in speed and on top of that the motor will be lugging.
I suspect it should normally run with a prop around 19".Be sure the motor is in excellent tune,Timing right and advancing as it should.
Throttle opening all the way? Good compression.Prop in excellent condition.
 
F

fishrdan

Admiral
Joined
Jan 25, 2008
Messages
6,989
Re: the right prop

tsport said:
oit wieghs around 25-2900 lbs loaded
Click to expand...

Did you have the boat weighed (truck scales) or is this just a guesstimate?

steelespike said:
Be sure the motor is in excellent tune,Timing right and advancing as it should.
Throttle opening all the way? Good compression.Prop in excellent condition.
Click to expand...

Soaked foam?

I agree with SS, the engine is turning within it's WOT RPM range, so the prop is correct as the boat sits right now. If you find something wrong, correct it, and then the engine overshoots the WOT RPM, then you can step up in pitch.
 
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