OVER-PROPPED

[bzz]

I JUST PUT A RAPTURE 21 " PITCH PROP ON MY FORCE 120. THIS WAS THE PITCH THAT WAS ON THE ORIGINAL PROP. THE BOAT DOESN'T SEEM TO PERFORM ANY BETTER. AM I MISSING SOMETHING? SHOULDN'T I GET BETTER PERFORMANCE. AT 5000 RPM I'M RUNNING ABOUT 40 WITH A MINIMAL LOAD. THE BOAT IS A 19' SEA-PRO

 

[JUSTINTIME]

Re: OVER-PROPPED

what is the rated max rpm of the motor, u want to be with 100-200 rpm of this

 

[steelespike]

Re: OVER-PROPPED

What was the speed and rpm before the new prop?
Is your speed on a GPS?
I'm not an expert but if your going from aluminum to stainless you generally need to drop in pitch.
I think your max RPM is rated at 5,000.
Most shoot for an rpm at least 200 above the max.
That said you are in the neighborhood and at 40mph
I would say close on speed.
Before you fool around too much you should borrow a tach and confirm your rpm and get your speed on a GPS.
Proper engine set up(height and trim) and weight distribution could add a couple of miles MPH.
If you want the best prop help go to the prop forum.

 

[JB]

Re: OVER-PROPPED

Prop forum

 

[bzz]

Re: OVER-PROPPED

What was the speed and rpm before the new prop?
Is your speed on a GPS?
I'm not an expert but if your going from aluminum to stainless you generally need to drop in pitch.
I think your max RPM is rated at 5,000.
Most shoot for an rpm at least 200 above the max.
That said you are in the neighborhood and at 40mph
I would say close on speed.
Before you fool around too much you should borrow a tach and confirm your rpm and get your speed on a GPS.
Proper engine set up(height and trim) and weight distribution could add a couple of miles MPH.
If you want the best prop help go to the prop forum.

 

[irv64]

Re: OVER-PROPPED

Excuse my ignorane but is this not the prop forum? If not could someone guide me to the right spot? I looked and couldn't see anything that this section for props. Thanks.........Irv64

 

[walleyehed]

Re: OVER-PROPPED

Yes, NOW you are in the prop forum...
Your engine max should be 5250-5300.
If we're going for max performance, we may have to lift the engine up to the next set of mounting holes to get some gearcase out of the water to decrease drag.
The Rapture is going to pull harder and not give huge number gains if the set-up isn't close to correct to start with.
I have a buddy here with an 18ft Bayliner and the 120 Force, and our best RPM/Performance comes with a 17 pitch, but we are at 3500ft elevation...at 600ft we get about an even 5200 with a 19P (on an 18ft Boat).
We can likely improve your performance if you're willing to pull a few bolts and raise the engine.