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post #5 of Old 11-16-2019 Thread Starter
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Re: Flexofold prop performance

Originally Posted by TakeFive View Post
Your experience is similar to my first season with my new 3-blade 15x9 FOF prop. The FOF has a higher EAR than most "sailer" type props (the ones with narrower blades for less drag), making it more efficient when motoring. And, of course, it's much less drag when sailing, so you're getting the best of both worlds. [EDIT: After looking at your "before" picture, it appears that you didn't have a "sailer" type prop, but a more typical powerboat-like prop.]

I too noted less prop walk and a little less thrust in reverse. But I'm easily able to apply more throttle in reverse when I need it.

You should note that getting higher speed at a given RPM is not necessarily a good thing. Props don't create more power, they just transmit your motor's power to the water. The price you pay for getting higher speed at a given RPM is greater load on the motor, which if excessive could lug the motor, leading to carbon deposits and difficulty making way if you're motoring against strong winds. The key test is to make sure your motor gets to the manufacturer's rated maximum RPM at full throttle (with clean bottom and smooth water). If not, your motor isn't able to produce full power and will strain when you need to have that power.

I had been warned that many have to reduce their pitch by an inch or so when switching to a similar diameter FOF. My motor is rated at 3000 RPM maximum, and I was getting 3400 at full throttle with my old 9" pitch "sailer" prop, so I stuck with 9" pitch on the FOF and I now get 3200 RPM at full throttle. This is still a little above 3000 RPM, but Maine Sail advises that it's better for max RPMs to be a little too high than too low.
Full throttle is 3200rpm with the FoF which is the same max rpm I got with the fixed prop. The big difference was 1 knot higher boatspeed. I can only assume the better boatspeed is due to a superior blade design. It certainly wasn't overloading the engine or it wouldn't have been reaching the same max rpm.

I am curious, what kind of performance increase did you notice when you switched to the FoF?

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2011 Jeanneau 39i Azura

Last edited by SchockT; 11-16-2019 at 03:47 AM.
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