# best propeller pitch



## boater55 (Sep 16, 2012)

i am thinking about buying a 15 hp evinrude motor but it needs a propeller
i want to get a 4 bladed propeller and was wondering what pitch to get they are 9.25x 7,8,9,10 or 11
Thank You


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## Johny25 (Sep 16, 2012)

Far to little info to even begin to give advice. What year motor? What prop was on it? What are you putting it on? What is the purpose, trolling or main motor? What were the RPMs before and why do you want a 4 blade.....etc.

A 4 blade will give more lift to a boat and better holeshot but will take away from top end. Also they bite harder and have more drag than a 3 blade so always go down in pitch.But since you don't have any data from any prop you are just peeing into the wind and guessing.


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## PATRIOT2 (Sep 17, 2012)

Put me down for the 3-blade 8 pitch. (middle of the road)


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## Johny25 (Sep 17, 2012)

PATRIOT2 said:


> Put me down for the 3-blade 8 pitch. (middle of the road)



Did you mean 4 blade 8 pitch? Stock props for a 15hp are usually 9.5X10 so in theory an 8 or 9 pitch 4 blade could be the right solution but once again we have no info to start from and it is merely guessing


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## PATRIOT2 (Sep 19, 2012)

Johny25 said:


> PATRIOT2 said:
> 
> 
> > Put me down for the 3-blade 8 pitch. (middle of the road)
> ...


Nope, I'm just going by the owners manual for my 15HP.


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## Johny25 (Sep 19, 2012)

Huh what year and brand motor is that for?


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## PATRIOT2 (Sep 19, 2012)

1987 Nissan NS15


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## Johny25 (Sep 20, 2012)

You have a 1.85:1 gear ratio. That is why you have to run such a low pitch prop. Johnson/Evinrude 15's have a 2.41:1 gear ratio and can turn a higher pitch prop. 

With your gear ratio and RPM and range (4750-5500) you can turn an 8 pitch 3 blade at 5500rpm and hit 19mph with a 15% slip but if you stick that same 8 pitch on the J/E you will only get to 15mph at 5500rpm at 15% slip. See what I am saying, two completely different motors and setup needs. Fact is the J/E would turn that 8 pitch at way too high an RPM unless it is on a pontoon or a heavy boat. The J/E is rated for 5500-7000rpm. I am assuming he has a 70's, 80's or 90's Evinrude mind you.

His J/E most likely came with a 9.5X10 prop which is typical for these motors. Basically he has to turn a 10pitch at 5500 with his gearcase to get close to what you get with an 8 pitch


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## Johny25 (Sep 20, 2012)

Usually the 7 and 8 pitch props for the J/E's are for when you use the motor as a kicker on a heavy boat for trolling. The 9 and maybe 10 pitch would be for a heavy tin boat (14-16') and the 11 pitch and up would be for light applications on 10-12' lightly loaded tins. Hell even a bare bones 14' tin would fly with a 11 pitch on a 15hp J/E. 

This is not set in stone, just a generalization of what these different pitched props could be used for. To get real technical I need to know the motor year and brand, GPS readings of current prop, prop specs (pitch, number of blades and diameter), RPM readings from a reliable tachometer and boat setup/brand/model


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## bcbouy (Sep 20, 2012)

9 1/4 x 11 j. i have a 2011 15 2 stroke yami.when i bought it i asked them what prop will be best,and they told me its on there now.didn't even try to upsell me.keep in mind a 15 hp is not exactly a monster in the power department.


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## Johny25 (Sep 20, 2012)

YOU CANNOT RECOMMEND A PROP FOR SOMEONE WHEN YOU ARE TALKING ABOUT A COMPLETELY DIFFERENT MOTOR WITH A COMPLETELY DIFFERENT GEAR CASE!!!!!! 

You have a 2.08:1 gear case on that Yamy and a totally different RPM range so your input about your motor has NO bearing on the OPs question.......I just got done explaining this 2 posts above. Your giving bad info to someone with a totally different engine


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## Pappy (Sep 21, 2012)

Johny25 said:


> YOU CANNOT RECOMMEND A PROP FOR SOMEONE WHEN YOU ARE TALKING ABOUT A COMPLETELY DIFFERENT MOTOR WITH A COMPLETELY DIFFERENT GEAR CASE!!!!!!
> 
> You have a 2.08:1 gear case on that Yamy and a totally different RPM range so your input about your motor has NO bearing on the OPs question.......I just got done explaining this 2 posts above. Your giving bad info to someone with a totally different engine



You learn well, grasshopper!! Keep it up.


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## Johny25 (Sep 21, 2012)

I am not sure if you are applauding my grouchy response or that my prop info was good :lol: Now that was funny right there :mrgreen:


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## turbotodd (Sep 21, 2012)

For that matter, an accurate prop suggestion would almost impossible without knowing the boat, how much weight, how it's loaded, motor height, current pitch/dia/ and RPM-among other things.

Find a stock 3 blade, get a tach and go run around on the water. Then tell us what the RPM is and we can get pretty close.

Dad's 1432 J/E 15 runs a Solas Aluminum 9" 4 blade. 4 blade for getting it out of the hole quickly because sometimes it's loaded down pretty good.


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## bcbouy (Sep 21, 2012)

Pappy said:


> Johny25 said:
> 
> 
> > YOU CANNOT RECOMMEND A PROP FOR SOMEONE WHEN YOU ARE TALKING ABOUT A COMPLETELY DIFFERENT MOTOR WITH A COMPLETELY DIFFERENT GEAR CASE!!!!!!
> ...


holy crap dude,lighten up


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## Pappy (Sep 22, 2012)

bcbouy said:


> Pappy said:
> 
> 
> > Johny25 said:
> ...



Really not a question of "lighten up" ......When someone offers information that really doesnt't have a clue what they are talking about it could cost the OP money if he takes that incorrect advice. The only similarity between the two 15hp engines is the numbers on the cowling.


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## Charger25 (Sep 22, 2012)

I love this forum :LOL2:


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## New River Rat (Sep 22, 2012)

I fish a lot of bedrock, ledges and shoals, so that was something else I figured into MY equation. I need to get the assend up in a hurry sometimes, so a lower pitch was my preference. I don't need WAO on my boat.


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## boater55 (Sep 22, 2012)

the motor is a 1976 evinrude it will be the main motor on my 12 ft v hull boat i am looking for the propeller that will deliver the most speed the motor does not have a propeller on it and i don't know what it had on it i only wanted a 4 bladed propeller because i assumed id would increase the speed


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## Johny25 (Sep 22, 2012)

A 4 blade will not increase speed, it will take away from top end. Since it is a 76' model and does have the 2.41:1 gear case and RPM range 5500-7000k I would recommend a 3 blade 10 pitch prop if your putting it on a 12' tin. This would probably be a safe starting point to get some info. From there you can adjust in pitch to get optimum performance. But you have to start somewhere and cannot expect to get the perfect prop on the first try with out any data to go by. All we can do is give you an educated guess from our experiences. 

If you can turn a 10pitch at 6250-6500rpm you should see numbers around 20-22mph assuming a 15%-18% slip


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## boater55 (Sep 22, 2012)

the stock propeller is a 9.25x 10 (it is three bladed) 
does that sound like a good propeller to start with?


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## Johny25 (Sep 22, 2012)

Johny25 said:


> A 4 blade will not increase speed, it will take away from top end. Since it is a 76' model and does have the 2.41:1 gear case and RPM range 5500-7000k I would recommend a 3 blade 10 pitch prop if your putting it on a 12' tin. This would probably be a safe starting point to get some info. From there you can adjust in pitch to get optimum performance. But you have to start somewhere and cannot expect to get the perfect prop on the first try with out any data to go by. All we can do is give you an educated guess from our experiences.
> 
> If you can turn a 10pitch at 6250-6500rpm you should see numbers around 20-22mph assuming a 15%-18% slip





boater55 said:


> the stock propeller is a 9.25x 10 (it is three bladed)
> does that sound like a good propeller to start with?



Yeah that is what I just said....... the 9.25 is diameter and it has little bearing on RPM performance unless you jump in large increments. So a 9X10, 9.25X10 or a 9.5X10 will be fine. Here is a good site for props at a good price and these will all fit your motor
https://boatpropellers.iboats.com/Evinrude-Outboard-Propellers/?pitch=10.00&chart=7&engine_id=23&cart_id=504378492


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## highgeardaddy (Sep 22, 2012)

Sorry for the stupid question but how do you rig up a tach to check your WOT RPM. Are there automotive tachs. that you can clip on just for these quick water tests?


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## Johny25 (Sep 23, 2012)

A typical auto tach will not work on a two stroke. They sell "tiny tachs" for about $50 that read two stroke engines and all you have to do is wrap the wire around a plug wire.


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## Charger25 (Sep 23, 2012)

boater55 said:


> the stock propeller is a 9.25x 10 (it is three bladed)
> does that sound like a good propeller to start with?



I would say yes. I've got a 78 Evinrude 15 hp it was turning a 9.25 X 8 prop. That set up got the 16 ft lowe (v-hull) up on plane very well. With approximately 575 lbs ( persons,motor & gear) I was able to out run a bud of mine in a 14 ft with a 8 hp (semi-V) I ordered a 9.25 X 11 prop because I'll mostly be running it on the 14 ft. Haven't tried it out yet though. I agree with Johny25 and IMHO, your 15 W/ a 9.25 X 10 on the 12 ft should FLY !


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