Does NGR prop like pitch or RPM?

Airboat propeller discussion.
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Tony480
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Re: Does NGR prop like pitch or RPM?

Postby Tony480 » Sat Aug 20, 2016 10:07 pm

Your looking for more speed and a lower cruise rpm and that's not necessarily gonna come from either the box or prop...your hull and motor has a lot to do with it

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OneBFC
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Re: Does NGR prop like pitch or RPM?

Postby OneBFC » Sat Aug 20, 2016 11:14 pm

Stock turbo ecotec makes max power below 5400 rpm. Thus, 2.38 box makes sense.

Though I no longer use a stock turbo and could benefit from a 2.68, I just can't justify the cost. This boat goes fairly well as it is. Some interesting links in my signature to see it running. People will bag on the "ecoturd" but I have had excellent results with mine. Others have too, but some have not been as happy.

Anyway, don't want to stir up anything in your thread. :D

For what it is worth, Tony is right I think. Setup could well be your gremlin and not the prop or engine and reduction.
-Russ
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The only thing stopping you is FEAR
400hp Ecotec, 12x7.6 DBDO, 4B Falchon, 2.3 OX,70+mph,10mpg,water = purely optional
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SWAMPHUNTER45
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Re: Does NGR prop like pitch or RPM?

Postby SWAMPHUNTER45 » Sun Aug 21, 2016 8:27 am

X3 set up

If your not after speed set the prop where you get both your target rpm and best efficiency and enjoy the ride.

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Des Moines Boater
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Re: Does NGR prop like pitch or RPM?

Postby Des Moines Boater » Sun Aug 21, 2016 8:41 am

Thanks Swamphunter45. That sounds like good advice. I'm not after speed but it would be sweet to cruise at 30-32 mph turning 2600 rpms, like Tony. The prop is only turning 970 rpms which seems incredible. I'll play with is some more and find the sweet spot.

OneBFC, on my 383 I make 400 foot pounds at 4000 and max out at 440 foot pounds at 5000 rpms. After 5000 the curve starts down and at 5800 I'm back down to 400 foot pounds. There is sure a lot to learn using a car engine. Aircraft engines were so simple.
13' 6 Lazer, 383 SBC 425 hp, 2.7 Ballistic, 3 blade 80 NGR

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Deano
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Re: Does NGR prop like pitch or RPM?

Postby Deano » Sun Aug 21, 2016 10:04 am

Trying to compare and replicate Tony's results only defines in clear fashion what you can not do.
You only have 75% of the power he does, aren't turning the RPMs, and have a smaller prop.
Perhaps this expectation/desire is part of what is leading to your misunderstanding.

Different props have different power bands and/or work best at different rpms.
As Dave explained, the NGR blades excel at higher RPMs where the winglet can do its job.
As such, it looks to me like that is not the best blade choice if your ultimate goal is low rpm cruising.

If low rpm cruising is your goal, given your gear ratio, a wide blade prop such as a SuperWide or a Maximus pitched to turn 54-5600 rpms would be a much better choice and get you in the neighborhood much quicker with less mental anguish.

In spite of that sounding like it is moving the aguish to your wallet, no amount of effort on your part will get any prop to operate any differently than how it was designed or what the laws of physics will allow.

You have near new, very popular blades. I wouldn't think it would be that difficult or costly to move sideways into a set of R blades or SuperWides since either ones would work in your existing hub and offer you a much fatter likelihood of attaining the end it seems you are after.
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but it is not the path to knowledge; it has no place in the endeavor of science."
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Re: Does NGR prop like pitch or RPM?

Postby Des Moines Boater » Sun Aug 21, 2016 11:16 am

Great advice and opinions. Thanks for the replies.
13' 6 Lazer, 383 SBC 425 hp, 2.7 Ballistic, 3 blade 80 NGR

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Tony480
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Re: Does NGR prop like pitch or RPM?

Postby Tony480 » Sun Aug 21, 2016 4:46 pm

Your hull is what's killing you

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Re: Does NGR prop like pitch or RPM?

Postby Des Moines Boater » Sun Aug 21, 2016 6:39 pm

I agree Tony. I wish I had an 8 foot instead of a 7 foot wide hull. My prop was set at 16 degrees, so I increased it to 17.5 and I'm getting closer to your numbers, so, I'm happy with what I have.
13' 6 Lazer, 383 SBC 425 hp, 2.7 Ballistic, 3 blade 80 NGR

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Re: Does NGR prop like pitch or RPM?

Postby CarMotorBarge » Sun Aug 21, 2016 6:48 pm

Yes, lowering your engine WOT by increasing pitch will improve your cruise RPMs. However, this will decrease the amount of dry running you can do. Also you increase the chances of an EcoTurd out running you. :shock: :stirpot: :stirpot: :stirpot: :stirpot: :stirpot:
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