# Different prop pitches



## AUPKT (Mar 10, 2009)

How extreme of a difference would going from a 17p to say a 19 or 21. My boat has no problem revving out even with a large load at a 17p. Just wondering if I could expect drastic bogging down with a 19 or 21. Just looking for a little more top speed for fishing. I also don't want to spend a bunch on props just to test it out.


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## Mikvi (Mar 11, 2008)

Are you exceeding max RPM for your motor with the current prop? If not, you have the right prop. If you are over-revving at full throttle, increase the pitch. Increasing the pitch on a motor won't do much good for you unless you have the power to turn it.


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## Clam (Nov 10, 2007)

I think the rule of thumb is 200 rpms per pitch. So if you went from a 17p to 19 p you would loose 400 rpms.


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## AUPKT (Mar 10, 2009)

I don't have a tach for it but the motor is extremely torquey all the way up, which isn't a bad thing, but it can catch you off guard standing up driving. I just wanted to mellow out the torque and gain some top speed. The 17p is the factory prop.


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## Donut slayer (Jan 16, 2009)

You need a tach to properly prop a boat. Cant go by feel.


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## X-Shark (Oct 3, 2007)

> i think the rule of thumb is 200 rpms per pitch. So if you went from a 17p to 19 p you would loose 400 rpms.
> Share


x- 2



> you need a tach to properly prop a boat. Cant go by feel.


x- 2


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## AUPKT (Mar 10, 2009)

Well today I finally realized what some of my problem has been. Keep in mind it's a used but new to me boat, I bought it last weekend, the prop on it now is not the stock prop but a 15p. The guy used the boat to troll for stripe and at idle he was going to fast with the 17p. So I will be purchasing the correct pitch at this point.


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## Donut slayer (Jan 16, 2009)

What size boat? Motor?


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## AUPKT (Mar 10, 2009)

18' aluminum CC with a f90


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## Clam (Nov 10, 2007)

I would go to yamahas website and check for boat test under the f90 and see if there is a hull similar to yours. It will show you top speed, rpm range, load and which prop they tested with


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## AUPKT (Mar 10, 2009)

I did and thats where I came up with the 17p prop being stock prop. But since I've had it the boats top speed was low but had a lot of umph. Thats when I looked today and saw that the prop on it was a 15p. There is a performance report for this exact boat and motor and my top speed was 4-5 mph lower. Getting the stock pitch should get me to where I want to be.


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## Donut slayer (Jan 16, 2009)

17 would be about right for that boat. I have a 16' fiberglass bass boat with a 1984 90hp evinrude. I run a 19 on mine and turn right at 5800 with just me and a tank of fuel. Loaded to fish, wife and dog, about 5400. I have a raker 18 that I tried, 6200 with just me. :w00t: Just a little on the high side for WOT, but man what a hole shot.


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## RMS (Dec 9, 2008)

You need to keep in mind that by summer time, your motor won't make quite as much power as it does right now, because warmer, more humid air will make less power, since it is normally aspirated. Based on numerous past experiences the difference can be significant.
For example, I had a Yamaha f150 on a bay boat that would lose 300-500 rpms from winter to summer.


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## X-Shark (Oct 3, 2007)

Sounds about right for a 18 alum with a Yamaha F90 on it...Cause I run a 3 X 14 X 18 on my DF-90 Suzuki....Suzuki's are geared lower, so they can swing a larger diameter and more pitch.


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## Final Contender (Mar 18, 2014)

Stock prop? Lots of new boat are sold with a prop that will make it fast for the sea trial. Light with fuel and a light load. Then you get it home, load it up, fuel it up and it is no kidding slow, Stock prop has to much pitch and wont turn max rpm! Then you need a different prop. If you are turning rpm's at the top of your range and want more speed, take the prop you have (if its SS) to a good prop shop and have them put more cup in it. This will produce more mph and drop your rpm a bit.


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## AUPKT (Mar 10, 2009)

I got it all figured out.


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