can i not make an octura run with a prather?

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1

1BS

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I keep reading about how good these octura props run, I have tried both the 440 and the 442, and after 5 props each i cant make them run with my best 220 prather... thinned, balanced, sharpened, tweaked, cut down, added pitch, i have tried it all. Is there something i am missing here? :blink: the prathers consistently run 5 mph faster than any octura... speed is recorded with a gecko gps in the boat with an almost empty fuel tank and no extra lead in the front (in other words, race weight) all test run with a bandit tunnel- rossi powerhead/lawless lower :D I think the rossi still needs some pipe work, but it runs good.
 
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1BS,

The Prather 220 has a higher pitch ratio than the X440 and X442. Have you tried an Octura X640 or X642? They have a higher pitch ratio than the Prather's.

Also, did you try running your pipe shorter with the smaller Octura props at all? Sometimes a smaller prop and a shorter pipe can do wonders! Not saying this is the answer, but worth trying IMO.

One of my Fave props on my 21 O/B was a Prather 220, reduced diameter and back cut. Handled rough water really well. Not the fastest prop on good water. cupped Octura 1440 was faster.

Tim.
 
well i don't know if this will help, but i run an s-215 my avg. lap speed is about 35 mph.

allen
 
Hay Tim.

I'm new to all these but..... If you put a smaller pitch prop on and shorten the pipe, how dose that increase the top speed? By shortening the pipe you lower the revs that the pipe comes on and then lower the useable revs for the power band? I have no idea! I've just read a couple of things and never used a pipe but I'm interested on how it works.

Cheers

Chris
 
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Shortening the pipe raises the peak power point, effectively increasing motor rpm. It also reduces torque a bit, but since you're spinning an effectively smaller prop that is an easy trade-off. Spinning the prop faster may result in a higher top speed. No guarantees - as stated - but it's worth a try.

The real issue is the thinking that the two props were the same, when the Prathers actually have more pitch. Kinda like running your car in 5th gear and wondering why it goes faster in 6th. That's why this forum is so great! :)
 
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Yeah - what Jay said. Thanks Jay. B)

As you shorten the pipe, the peak rpms can increase, so by going to a smaller prop AND shortening the pipe, you are spinning the smaller prop faster and therefore pushing more water.

As I said earlier - this isn't always the way to go, but on 21 engines, they make their power @ high revs. Also, torque can induce wierd handling effects on a tunnel hull. So it's worth trying in my opinion.
 
i love this place, its the only place to find honest information without all the extra junk. so much information to absorb and i've only seen the water twice. all i need now is a pipe. which two props would you guys use to do the real comparison between the octura and prather on a 3.5's?

nate
 
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1BS,

You would have to try a Octura X-642 to get close to your Prather 220.

Octura Propellers

1440= 39.9 mm x 55.8 mm w/1.4 Pitch Ratio

X-440= 39.9 mm x 55.8 mm w/1.4 Pitch Ratio

X-442= 41.9 mm x 58.7 mm w/1.4 Pitch Ratio

X-640= 39.9 mm x 55.8 mm w/1.6 Pitch Ratio

X-642= 41.9 mm x 67.1 mm w/1.6 Pitch Ratio

Prather Propellers

P-215= 40.6 mm x 63.5 mm w/1.6 Pitch Ratio

P-220= 43.7 mm x 66.0 mm w/1.5 Pitch Ratio

I think if you tried a pitched 1440 B/C from Grim or myself you would be

faster. I think you don't have your propellers cupped for maximum

performance yet. What kind of speeds are you going with the P-220?

The 1440's are going in the 50's without any trouble at all. If you need any

help, let me know, I would be happy to make you faster. :D

You may want to try a Carbon OB Pipe from S.P.P. I have a few in stock

still.

Thanks, :)

Mark Sholund
 
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Prather 220 Vs Octura? Somewhere between an X442 and a X642.

I prefer the Prather 215 when stock to the 220. The 220 modified is a nice prop.
 
im running 52 relatively consistently with the prather, best of 47 with the octura. remember, thats straight line with a mod motor, I think once the motor gets a half gallon through it, i might pick up some r's... the prather 220 has cup added to it, thinned blades and is a good bit cut down in diameter, it hooks up and runs good. interestingly enough, my slip numbers are just about the same between the props, but the extra pitch of the prather gives me the speed. Today I really boffed at lunch running the boat- the water tube mount came loose and the water tube got into the prop, bent my cavitation plate up, twisted the flexshaft and ripped the teflon tube all to bits, :( luckly my stainless prop is unschathed...

hopefully fred (lawless man) will get the e-mail I sent him. I have something going on thursday and friday, and dont really want to "rig" the boat to run right.
 
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1BS said:
I keep reading about how good these octura props run, I have tried both the 440 and the 442, and after 5 props each i cant make them run with my best 220 prather...  thinned, balanced, sharpened, tweaked, cut down, added pitch, i have tried it all.  Is there something i am missing here? :blink: the prathers consistently run 5 mph faster than any octura...  speed is recorded with a gecko gps in the boat with an almost empty fuel tank and no extra lead in the front (in other words, race weight) all test run with a bandit tunnel- rossi powerhead/lawless lower  :D   I think the rossi still needs some pipe work, but it runs good.
87829[/snapback]

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Click to expand...
IBS

You have mentioned that you are using a Prather stainless steel prop. Octuras of course are all berilium copper. Did you know that Berilium is more flexible than Stainless? Terry Prather told me this, so I conducted an experiment using the Prather stainless vs the Prather berilium props. All factors being equal, the stainless prop had better speed than the berilium.

Just my two cents. ;)
 
Jack,

How did you measure the pitch difference between the two materials?

Not many casted propellers come out alike. This would be a difficult test

to get the propellers the same,but I do believe you. Now with CNC machines

they could be produced the same,but man would they be expensive. I would

like to hear more about your tests Jack,could you PM me your number?

Thanks,

Mark Sholund
 
well- changed the pipe on the motor and the 220 ran like DOODIE.... ran the 440 with a bit of cup and it woke the boat up. now I am running the same speed, but more RPM and better acceleration. :lol:
 
Bingo!

Now try a cupped and Back cut 1440, get it trimmed right (they are a bit different to the X series props) and hold on!
 

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