Prop size question

[Bluetick1955]

I have a G# PF165 with a 4 stroke yamaha 9.9. Of course very slow. The prop is a 9¼ x 11¼. A number of years ago A guy from G3 told me I could try a 9¼ x 10½". It may help

Would this difference have much effect in your opinion?

 

[PATRIOT]

Just for reference, here are outlines of the 2 props I run on a 15HP Nissan 2-stroke. In my case the 9.8P makes a difference, speed wise. The chart is from my owners manual. They both have the same diameter obviously but the higher pitch has more prop surface in the water.

 

[Bluetick1955]

Thanks fro the reply so if I'm understaning you getting the 10½ wouldn't help?

 

[crazymanme2]

Not all props have more blade area with the larger pitch.

 

[tnriverluver]

About the only way to know if the prop will help or not for sure is to try one. Either find a dealer that has one in stock that will let you test it or fork up the cash and buy one. Somewhat like gambling, sometimes you win, sometimes you lose but at least you will now have a spare prop for those unforseen breakdowns.

 

[turbotodd]

IIRC, most of the F9.9's came with a 9 1/4 x 9. Might try the stock prop and see what it does. It's been my experience that a lot of the time, the stocker will perform as good-sometimes better-than a lot of aftermarket props; especially if changing the pitches.

It's entirely possible that it could be so severely over-propped that the little engine just can't develop enough torque to spin that 11 1/4". If that was the case, dropping a pitch or two may put it back where she "wants" to be.

Any idea what the current RPM is at wide open throttle and/or what the maximum speed is?

 

[Bluetick1955]

IIRC, most of the F9.9's came with a 9 1/4 x 9. Might try the stock prop and see what it does. It's been my experience that a lot of the time, the stocker will perform as good-sometimes better-than a lot of aftermarket props; especially if changing the pitches.

It's entirely possible that it could be so severely over-propped that the little engine just can't develop enough torque to spin that 11 1/4". If that was the case, dropping a pitch or two may put it back where she "wants" to be.

Any idea what the current RPM is at wide open throttle and/or what the maximum speed is?

Have no idea RPM. Boat speed is 8 mph with 2 persons, According to G3 in 2003 the hull weight is 760lbs. This is the prop that came on the engine new on this boat

 

[rickybobbybend]

Knowing current rpm at wot is important. Absent that, I suspect you will need a bigger mill if you want a significant increase in performance.

 

[muskiemike12]

If you bought it that way, the dealer set it up wrong. You should be running a 8" or 9" pitch on that heavy of a rig. Have the dealer reprop.

 

[Bluetick1955]

Getting confusing for me. I'm just trying to get a couple more mph if possible

 

[turbotodd]

The F9.9 came with ~ 9" pitch...or...at least the 2013 model I looked at today has one on it. Should be white in color (painted aluminum). I can't see a F9.9 pulling 700-some pounds of hull weight with anything more than that. Perhaps the 11 1/4" is too much pitch, and dropping down to say a 9" pitch would certainly make it feel much better. Might even pick up some speed. If you already have the 10 1/2, it's worth a try. If not, I'd try a 9" or real close to 9".

But without RPM data, it's a guess. A slightly educated guess based on my previous experiences with an F9.9, but a guess nonetheless. If you had a tachometer rigged up somehow, whether it be a portable handheld tach or even one of these https://tinytach.com/gasoline.php, it would be a much more educated guess.


I run a 11 1/4" on my 25 HP, and my hull weight is 354 lbs. Your 9.9 is trying to turn basically the same size prop but with less than 1/2 of the power and close to twice the weight, assuming your prop is a 11 1/4" pitch. I have not seen a listing for 11 1/4" for the F9.9's; but I may not have looked close enough.

What is the maximum horsepower rating for your PF165? I could not find it online anywhere.

 

[Bluetick1955]

The F9.9 came with ~ 9" pitch...or...at least the 2013 model I looked at today has one on it. Should be white in color (painted aluminum). I can't see a F9.9 pulling 700-some pounds of hull weight with anything more than that. Perhaps the 11 1/4" is too much pitch, and dropping down to say a 9" pitch would certainly make it feel much better. Might even pick up some speed. If you already have the 10 1/2, it's worth a try. If not, I'd try a 9" or real close to 9".

But without RPM data, it's a guess. A slightly educated guess based on my previous experiences with an F9.9, but a guess nonetheless. If you had a tachometer rigged up somehow, whether it be a portable handheld tach or even one of these https://tinytach.com/gasoline.php, it would be a much more educated guess.


I run a 11 1/4" on my 25 HP, and my hull weight is 354 lbs. Your 9.9 is trying to turn basically the same size prop but with less than 1/2 of the power and close to twice the weight, assuming your prop is a 11 1/4" pitch. I have not seen a listing for 11 1/4" for the F9.9's; but I may not have looked close enough.

What is the maximum horsepower rating for your PF165? I could not find it online anywhere.

Max HP rating is 40HP. We fish several lakes that have a 10HP limit. My father bought this boat because of it's layout and stability. I bought from him last year. I am a poor swimmer and I feel comfrtable in this boat. Stick steer so I don't have to move around.