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3 blade props

A

AirAg

Well-known member
I know on most auto engines, the max rpm to turn a 3 blade prop is 2450RPM. Is this the same for the aircraft 3 blade LH props? Or are these better to have them setup maxed out at 2700? The ones I am talking about are the Q series Sensenich, Waterwalker signature/cypress, and the super snapper from Whirlwind.

Brent
 
AirAg , the diameter of the prop determines the 'never exceed speed', but every manufacturer has a recommendation for what RPM at which their prop is the most efficient.
 
I turn all my props 2950-3000 rpm. LHR on aircraft, some say 2800 is the best, I think its bull, and I have proven to an prop builder before that 2800 isnt the best!
 
The low RPM of the auto props are due to the size and diameter of the props. I know some guys with Q-Series props that turn them over 3000 even up to 3200. I like to set them up to spin about 2900. If they turn less than that the customer says he only gets 2800 and I have to readjust them anyway to make them happy. Then I tell them to try it and we can adjust it later so he can compare.
 
Of course every boat setup is different but we have found if you set the Sensenich Q or H series to turn about 2750 on the trailer it will unload to about 2850 on the water.
This seems to give the best all around performance on most boats. Plenty of snap and good low end push. Both props are limited to a max rpm of 3000 by the manufacturer.

Correct me if I'm wrong, but I beleive Olf runs a 3 blade Q on his car motor with a belt drive, therefore for him 2450 is the sweet spot. It will be different on a direct drive boat.
 
Drspud, you're right ...... thanks for correcting that. I have a belt drive so I can run a little more pitch at less prop RPM.
I was concerned with overspeed. Glad you posted that 3000 rpm figure.
 
I'm running my S series super wide just a tad over 2000 rpm and the push and snap is unreal my motor is turning 5500 rps with a 2.68 gearbox.
 
There you go, Sniper. Crank in the pitch and then turn em slow. That's the beauty of reduction ..... more torque, bigger prop at less prop speed, less sound, and much better gas mileage. The snap is a bonus.
 
For my set up I only turn my engine at 4400 wot so my prop is only turning about 1650 but i like the way it pushes every boat is different and almost every combo is different so all you can do is look for you own sweet spot
 
The way I came up with that is I took my max rpm witch was 4400 and divided it by 2.68 and came up wit 1641. something
 
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