Prop question

badbean

Cadet
Joined
Jan 3, 2006
Messages
8
I have an '81 Mercury model 200 20 HP outboard. The 3 blade prop that comes from the factory with this motor is a 8 tooth spline 10" x 9 pitch Alum. prop. What would be the result if I put a 8 spline 9 3/4" X 5 1/2 pitch three blade Alum. prop on it? Would it work ok?
 

rickdb1boat

Supreme Mariner
Joined
Jan 23, 2002
Messages
11,195
Re: Prop question

Depends on what boat you're using the motor on and what the Wide Open Throttle RPM's are with your current prop. You risk overreving the motor if not propped correctly, as the 9 3/4" X 5 1/2 pitch prop will give you another 600 or so RPM's given the same load. A little more info would help us help you more..
 

badbean

Cadet
Joined
Jan 3, 2006
Messages
8
Re: Prop question

I am not sure what the RPMs are when it is wide open. I use the motor on a Polarkraft 14ft. duck hunting rig jonboat. I also use the boat in the spring/summer/fall for fishing and running a crab trotline.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,762
Re: Prop question

Going down in pitch increases engine RPM but would provide better hole shot and would move a heavier load but with a corresponding decrease in speed. Increasing pitch reduces engine RPM and has the opposite effect. Think of less pitch as selecting a lower gear in your car (more power but less speed). Conversely, more pitch is a higher gear (less power but more speed -- but only if the engine has the power to reach max RPM using a prop with that pitch). Without any idea what your engines WOT RPM is with the current prop, effect of prop changes is only a guess.
 
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