Question on max engine rpm with reduction belt?

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RedfireSVT
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Question on max engine rpm with reduction belt?

Postby RedfireSVT » Wed Jul 26, 2017 11:26 am

I have a 2.3-1 reduction belt and a Whirlwind Whispertip EX 79" or 80" 3 blade prop. The max prop RPM is 2500 so with that reduction belt what is my max engine RPM. 5200rpm?
16x8' 2014 Longhorn Custom
6.0L LS Motor
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br,lc,LA
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Re: Question on max engine rpm with reduction belt?

Postby br,lc,LA » Wed Jul 26, 2017 11:55 am

2500 X 2.3 = 5750 but target 5200-5300 on the motor as the prop will gain 200+/- rpm on the water.

Also what is your engine curve and where does it hit peak HP. That really dictates the target rpm.
2016 American Airboat's AirRanger pushed by an Airboat Pros 2015 1.4L GM Ecotec... "Nothin' as Fine as Hearing a Turbo Whine"

ffjpowell
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Re: Question on max engine rpm with reduction belt?

Postby ffjpowell » Wed Jul 26, 2017 5:59 pm

What he said. Also the prop will have a sweet spot together with the boat. Dont necessarily have to swing it to 2500. May work better at a lower rpm. Also depends on what u want the boat to do. More pitch better push, less pitch better top end; as a general rule. Good luck with it. Grab some tools n hit the water for a day of fine tuning and fun. B safe

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RedfireSVT
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Re: Question on max engine rpm with reduction belt?

Postby RedfireSVT » Wed Jul 26, 2017 11:47 pm

I just did a cam swap and I am going to have it tuned so I was wondering where to set the rev limiter. I want more push and not as concerned with top speed. It doesn't seem like it has much pitch in it right now.
16x8' 2014 Longhorn Custom
6.0L LS Motor
80" 3 Blade Whispertip
Love it!

eldorado
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Re: Question on max engine rpm with reduction belt?

Postby eldorado » Fri Aug 18, 2017 7:42 pm

Agree with br,lc. What is the engine? Reductions are relative to RPMs and torque. You need to know Peak RPM versus torque output. If you have not tested/ dynoed your engine and it is stock look it up on the internet and it will give you the numbers of peak RPM versus torque. There is no reason to run your engine any faster than the peak RPM versus torque because torque is what will push your boat.

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Deano
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Re: Question on max engine rpm with reduction belt?

Postby Deano » Sat Aug 19, 2017 8:11 am

eldorado wrote: . . . because torque is what will push your boat.

Get real clear in your mind what you think is "peak RPM vs torque" because
when OneBFC sees that statement, he will be sporting a different view. .. :)
"The suppression of uncomfortable ideas may be common in religion and politics,
but it is not the path to knowledge; it has no place in the endeavor of science."
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OneBFC
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Re: Question on max engine rpm with reduction belt?

Postby OneBFC » Sat Aug 19, 2017 1:49 pm

Can you rephrase this part of your last post? I can't tell for sure what you meant.

eldorado wrote:There is no reason to run your engine any faster than the peak RPM versus torque because torque is what will push your boat.


I suspect you meant to convey that there is no reason to turn the motor past its peak Hp as that is where you will make the most thrust.

Deano, I guess I do tend to respond to the Torque VS Hp threads quite often :D
-Russ
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Aeon
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Re: Question on max engine rpm with reduction belt?

Postby Aeon » Sat Aug 19, 2017 3:14 pm

pitch the prop to limit the motor, Do not worry about setting a rev limiter in the computer.

just make sure when they set the timing while tuning that they keep it reasonable. if you push it all the stock parts in your motor will come out and try to visit you.
17x8 Circle H powered by a TurnKey LS3, 2.55 ox box and 82" 3 blade JX

eldorado
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Re: Question on max engine rpm with reduction belt?

Postby eldorado » Sat Aug 19, 2017 7:54 pm


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Deano
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Re: Question on max engine rpm with reduction belt?

Postby Deano » Sun Aug 20, 2017 8:21 am

Sorry Russ, Looks look he didn't take the bait. :|

Do have to credit him though, for seeing the error of his ways before folks started stepping out to make popcorn. :thumbleft:

The twisted admission to be made here, is that I always find such discussions to be quite entertaining. :lol:
"The suppression of uncomfortable ideas may be common in religion and politics,
but it is not the path to knowledge; it has no place in the endeavor of science."
- Carl Sagan

br,lc,LA
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Re: Question on max engine rpm with reduction belt?

Postby br,lc,LA » Sun Aug 20, 2017 12:11 pm

Reductions are meant to get the motor into Peak HP Range... Torque means jack **** without RPM. HP is Thrust... the trick is to get the prop in its most efficient sweet spot when HP is peak.

In short, if only torque mattered everyone would be running direct drives and turning props at 3000 rpm because most NA motors make peak Tq close to that rpm.
2016 American Airboat's AirRanger pushed by an Airboat Pros 2015 1.4L GM Ecotec... "Nothin' as Fine as Hearing a Turbo Whine"


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