1995 Force 120 prop question...

G

GeneralQuarters

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I have a 1995 Force 120 outboard (long shaft) on my 1986 20' Proline walkaround which weighs in at 2500 lbs dry weight.

#1. What is my minimum and maximum RPM range for this motor?
#2. With the above information, can someone tell me what is the ideal prop for the intersection of speed and torque? I ask b/c I only get 22 or 23 mph right now. I'm pretty sure this engine can do more.
#3. What does WOT RPM stand for?
 
M

mpsyamaha

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Jun 8, 2007
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Re: 1995 Force 120 prop question...

That motor is only supposed to spin 5250 max... So you would want to prop it to turn right near that with a light load at WOT (Wide Open Throttle). I would say somewhere in the 4800-5200 rpm area would be good goal.

There is no way to tell what prop you need without some sort of baseline results from teh prop you have now. At the very least, we need to know speed, rpms at wot, and the pitch of the prop you have now. I would imagine that boat with 120hp should go 30-35mph with the right prop and assuming the hull is not waterlogged, engine is running correctly, mounted correctly, etc...
 
jestor68

jestor68

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Re: 1995 Force 120 prop question...

Your dry weight with the motor is 2875. Using 600 lbs for people and gear, and 25 gal of gas, the Mercury prop selector calculates your operating weight at 3646 and recommends a 13-1/4 X 17 pitch propeller.

A Solas Rubex aluminum prop would do a fine job on your boat.

The recommended full throttle rpm range is 4750-5250 rpm.
 
Frank Acampora

Frank Acampora

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Jan 19, 2007
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Re: 1995 Force 120 prop question...

Running correctly and propped correctly, I would expect that hull/engine to do about 35 MPH top speed with only the driver aboard. 3-5 MPH less with three people.

Try to test a couple of props and then when you find the best performer, go with the extra price of a stainless.
 
G

GeneralQuarters

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Re: 1995 Force 120 prop question...

jestor68 said:
Your dry weight with the motor is 2875. Using 600 lbs for people and gear, and 25 gal of gas, the Mercury prop selector calculates your operating weight at 3646 and recommends a 13-1/4 X 17 pitch propeller.

A Solas Rubex aluminum prop would do a fine job on your boat.

The recommended full throttle rpm range is 4750-5250 rpm.
Click to expand...

Thanks VERY much! This is a huge help.
 
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