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Prop-ology questions


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I have two props from Eric at OJ to demo. I wanted to find something in-between a 1235 and 2315, basically something that will work up to 2000' and at sea level. Decent cruising RPMs (similar to the 1235) but still enough low end to push 800's in each locker and a 650 lb bow bag for surfing (like 2315 will deliver). Not really concerned about wake boarding with the new Power Wedge 2 just about anything will work. I have the 410 engine. The 1235 is accomplishing this at sea level, but I think at 2000' it will be questionable with a full load of peeps and ballasted up for surfing.

OJ 925 is 14.75 x 13.75

OJ 948 is 15 x 14

If you had to bolt one on which one would you go with first?

Edited by Fman
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The 948. Only because I want to hear your review of it. My guess is that the butt dyno won't notice the difference between the two. But, I've been wrong before. Just ask my wife....actually, don't.

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Ok, 948 it will be.

Just to explain prop performance, first number is diameter - larger diameter, more grab, less chance of slippage. Second number being the pitch, a 14.5 would be more aggressive than a 14"? 15 x 14.5 would be more aggressive low end than a 15 x 14? the 14.5" would turn higher rpms? what does the cup dictate?

Edited by Fman
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The first number is diameter, yes, the larger the diameter AND larger blade area will provide more low end. The second number is the pitch. A 14" pitch prop will have better low end than a 14.5". Keep in mind, we, OJ and them, Acme, do not look at pitch the same. What we call a 14 they would call it something else. Cupping is the same way, we have different ways of adding cup as well as what we call it on the prop.

  • Like 2
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Eric, I thought pitch was pitch. How do you and Acme look at it different. Pitch is the theoretical distance the prop moves forward in one rotation. I'm looking for a prop between my 1273 and the 2315. The pitch goes from 14.25 to a 12 between those two. So, a 13 pitch should be ideal for me, that's why I was looking at your 945 prop.

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Me predicts 948 is too big. Me bets you'll struggle to achieve much over 5100rpm. You'll have slow launches when you go heavy with weight.

OJ 925 is 14.75 x 13.75 Would be my rec.

Good luck.

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I dunno. if the 945's 13" pitch "acts like" an acme 12" pitch (2315) then a 14" pitch might "act like" an acme 13" pitch, which could be about perfect.

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Very well could be.... But I will tell you that a 15" pitch in the OJ prop I just got, coming from an Acme 14.25" pitch, absolutely increased my idle speed.... Noticeably. It was a step up in real pitch.

I think the recent analogies on here of:

{OJ Pitch} = {comparable Acme pitch plus 1"}

might be over simplifying the Acme/OJ design differences Eric alludes to. I've only got a sample population of 6-8 Acmes vs 1 OJ, so take it for what's it's worth.

What I will say is OJ customer service is A+ akin to Brian at Exile, or Cory at Evolution.

Edited by nyryan2001
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Ryan,

The stock prop on my X-30 is fine but it doesn't really give me that yank out of the hole I like. It does 51 mph top speed on the 7.4 which is totally unnecessary for me.

Eric recommended the 14.75 x 15.75 with the 7.4. Will that be enough?

Other options would be moving up to lower pitch with the 14.75 or going to a 15 incher like the 845.

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After testing three props and looking at the numbers I had to call my pro prop guy and talk about why a lower prop 13.5 was not performing better then a higher pitch prop 14.

Dia will help with the push and better to hold speed when the boarder pulls hard to the side.

Pitch is pitch but is the pitch the same from tip to tip? NO not from the pic I'll post with more explanation.

Cup. To much cup can be a bad thing. From what I know and tested cup helps out most during the top end performance. Kind of helps pick the speed up.

I will have a report on my three props with speed, RPM and feel from the drivers seat tomorrow or today for most. LOL

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This is the data I posted up on a different thread

Did some testing of the last few weeks with the OJ 475, 915, 925. Test are with RPM and the seat of my pants. Over all each prop performs great with different needs in ballast setups. Boat being used is an 04 VLX with a few modifications than stock.

Speed

RPM

OJ 475

14.25x14

Ballast setup

Description

10

2000

no ballast 400lb front 3 people

21

2700

no ballast 400lb front 3 people

30

3700

no ballast 400lb front 3 people

35

4500

no ballast 400lb front 3 people

40

5000

no ballast 400lb front 3 people

45

5500

no ballast 400lb front 3 people

10

surfing

2300

750 rear lockers, 600 front, 600 front walkway, 750 in front of rear seat, 3 people

Pulled up to surfing speed with not much of a problem.

21 wakeboarding

3300

750 rear lockers, 600 front, 600 front walkway, 750 in front of rear seat, 3 people

The extra weight over my norm added time to hit WB speed.

The 475 has always been a great prop for wakeboarding and surfing with my stock (400lb lead front, 200 ski locker, 750 rear lockes) ballast and the wedge down but, when you add the 600 in walkway and 750 in front of rear seat then it had a harder time making it to plan.

Speed

RPM

OJ 915 14.75x14.5

Ballast setup

Description

10

no ballast 400lb front 5 people

21

3000

no ballast 400lb front 5 people

30

3900

no ballast 400lb front 5 people

35

4500

no ballast 400lb front 5 people

42

5200

no ballast 400lb front 5 people

45

no ballast 400lb front 5 people

10

surfing

2600

750 rear lockers, 600 front, 600 front walkway, 750 in front of rear seat, 5 people

Came up to speed without a problem.

21 wakeboarding

3500

750 rear lockers, 600 front, 600 front walkway, 750 in front of rear seat, 5 people

Had a little longer time to plan then with stock ballast but still did well.

This is a great prop for a little over stock boat that will give great hole shot but also keep the RPM down when crossing the lake. Still not a prop I would have for a stock boat and a large lake to cruse. By giving up this prop for one with on a large lake you would giving up a little better hole shot but would gain lower RPM at cruising speeds.

Speed

RPM

OJ 925 14.75x13.75

Ballast setup

Description

10

no ballast 400lb front 5 people

21

no ballast 400lb front 5 people

30

4400

no ballast 400lb front 5 people

35

4800

no ballast 400lb front 5 people

42

5500

no ballast 400lb front 5 people

45

no ballast 400lb front 5 people

10

surfing

2800

750 rear lockers, 600 front, 600 front walkway, 750 in front of rear seat, 5 people

Pulled hard to speed and had to pull back on throttle. Ended up only using part throttle to come to speed.

21 wakeboarding

3700

750 rear lockers, 600 front, 600 front walkway, 750 in front of rear seat, 5 people

This is pulled up to speed and held speed even when the rider pulled hard to the sides.

This prop is a stump puller that gives great hole shot for surfing and wakeboarding. In the end I will be going with the 915 as I don’t load my boat down with all this test weight for wakeboarding. I will be using most of this for surfing but with a little less in the front and rear floor bags as the wake is just perfect. This prop is great for an over weighted boat or in higher elevation.

Prop pitch. Both props have the same pitch but one is a 14.5” and the other is a 14.75” dia prop. Not sure if you can see it in the picture but both start off (at the bottom) with the same angle of pitch. The big difference is at the upper portion where the one (left side) prop tappers off with less of a pitch at the upper tip, thus giving it better hole shot and speed holding ability.

Prop on the left is the 915 and the right is the 475

post-235-0-90206600-1431584975_thumb.jpg

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  • 2 weeks later...

i have a 2014 vlx with the 330 - just got the 2419 acme prop - can't get surf wave to form with loaded boat and 2 plug and plays and all ballasts filled-any help

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