cupping prop

richardschmidt2759 · Jul 9, 2019

I am replacing the prop on my mainship1, 23/19 2350 wot now. I think it looks like it has a very slight cup in the wheel. any advantage to slight cupping on a 23 in wheel that turns 1.91 gear, about 1300 rpm at wot now?

fgarriso · Jul 9, 2019

What is the make, model, and HP of your engines.
Every is calculated from the engines back.

richardschmidt2759 · Jul 9, 2019

cup prop

I have a 200hp perkins in a mainship 1. 10 kt boat , but like i said 2350 wot ,book says 2400 wot, so close enough .1.91to 1 gear . type of motor has nothing to do with how I make the prop spin, just want to know if slight cup would help, or not .on small fast boats have much less slippage than .a larger heaver boat .I know that cupping on a small fast prop will make a big difference , just wondering what the effect it would have on a bigger slower prop ?

fgarriso · Jul 9, 2019

Richard,

The manual says 2400 RPM @ WOT. You are turning 2350 RPM @ WOT.
If the motor is not putting out BLACK smoke, or overheating after running at this for a few minutes. Then I would not change anything.

If it is producing black smoke then the injector pump is still giving it fuel and the motor can't turn any more. If so I would reduce the prop pitch by a 1/2" to reduce the engine load.

Lee,

Nomad Willy · Jul 9, 2019

This is just my opinion but I think cupped props don’t belong on trawlers. Probably more drag that thrust benefit.
The Mainship may be a fast enough boat to benefit from cup but I doubt it. And w a cruising boat cruise speed performance is the bottom line .. not top end.
Also I doubt cupping helps reverse thrust.

fgarriso · Jul 9, 2019

your correct

richardschmidt2759 · Jul 9, 2019

cup prop

eng is not lugging , no black smoke at any speed. most likely buy new prop same size, thanks

fgarriso · Jul 9, 2019

Is there something wrong with the prop(s) you have now?

cupping prop

richardschmidt2759

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richardschmidt2759

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Nomad Willy

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richardschmidt2759

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