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Gearing/prop selection

Blown72GN

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Ive been looking to switch to a 2 blade on my 20'howard from a 12×16 menkens 3 blade and would like any input regarding my current gear as well... setup is: 1150~hp th400 with 32's in a 12°... 12×16 3 blade. Gps'd 103.6 @7600rpm. Pulls hard but flattens out right around 100... like hits a wall... would a 11.75×16 2 blade help or am i running out of gear? Not trying to set the world on fire but... a lower cruising rpm would be nice as well as eclipsing the magical 110 mark...
 

obnoxious001

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Do you have a dyno sheet for the engine? Knowing where it makes peak power would help with gear selection. I ran 45's in my 20' Schiada that was set up for ski racing, approximately 1000 hp turbo engine (no dyno). 11 1/2 x 15 two blade and later 11 3/8" x 15. No GPS back then, but it would run under 6,000 where the engine was happy and could live longer.
 

obnoxious001

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By the way, while the two blade prop should give you more top speed, you can count on it to not be as smooth on take off, unless you were to step up to a Joey Grose CNC prop that costs a small fortune.
 

HighVoltage329

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I've always liked 2 blades. Not as much tail lift which helps carry the noise of the boat better at high speed.
If your boat likes the 3 blade and carries well then I stay with it and go up in gear.
I have the same HP and am running 48 gear and an 11-1/2 x 16 Grose and also have a Menkens the same size.
 

Blown72GN

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I've always liked 2 blades. Not as much tail lift which helps carry the noise of the boat better at high speed.
If your boat likes the 3 blade and carries well then I stay with it and go up in gear.
I have the same HP and am running 48 gear and an 11-1/2 x 16 Grose and also have a Menkens the same size.
I really like the way the boat takes a set and pull hard and controllable from 25-85mph. Carries the bow well. Would like to be able to cruize at a lower rpm tho... anything below 4k and the boat rides wet. Would like to be able to see 50mph at 3500~ would 39-43's be a good starting point?
 

obnoxious001

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I've always liked 2 blades. Not as much tail lift which helps carry the noise of the boat better at high speed.
If your boat likes the 3 blade and carries well then I stay with it and go up in gear.
I have the same HP and am running 48 gear and an 11-1/2 x 16 Grose and also have a Menkens the same size.
What rpm do you pull Bob? I could not find a used set of 48's when I put the 45's in. I had previously been running 43's and was looking for just a bit more top end.

Grose props are magic, aren't they? I did prop testing with Joe Mitchell after he bought Bob Stark's old Vector that I ski raced behind when it was new, prior to taking the boat apart to rebuild. When we got to testing the prop Joey sent, we looked at each other and knew the testing was complete, smoothest 2 blade I have ever felt!
 
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