Prop differences?

[RICHARD A. WHITE]

I have 2 props, both 3 blade, both aluminum. One is 9 1/4 X 11 and the other is 9 X 11. They do not have the same shape see photo below.
If I understand this right, the smaller OD will, or should give higher rpm, thus a bit more speed. Am I looking for 15 mph extra?…no…lol

Would the shape of the prop have and help or hindrance?

Thanks

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[outbdnut2]

I’ve found more speed with the style of your gray prop. I’ve always heard the style of your white prop is that way to try to keep weeds off…..but there are a lot of subtle factors that only a well trained eye can pick out, like the degree of cupping on each blade. I’d just try them both and see which works best. Let us know how they perform. Are these for 15-18 HP Johnson/Evinrudes?
Dave

[vintin]

I predict an increase in speed of 1.132 mph in fresh water and 1.126 mph in salt water. This assumes that you are in the northern hemisphere, born after 1/1/1950 and like cauliflower.

http://www.marineinsight.com/naval-arch … er-design/

[frankr]

Yeah, they called the curvy one a semi-weedless prop. There is no such thing in Florida, but let us know how it works out up there.

[RICHARD A. WHITE]

quote VinTin:

I predict an increase in speed of 1.132 mph in fresh water and 1.126 mph in salt water. This assumes that you are in the northern hemisphere, born after 1/1/1950 and like cauliflower.

http://www.marineinsight.com/naval-arch … er-design/

Epic

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[RICHARD A. WHITE]

I had thought the white prop was what would be semi-weedless, and the 1/4 in OD difference I did not think would make much of a difference, but the cupping or lack of is what I was wondering about… I will take them both and GPS each on a run

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[reivertom]

The type on the left has more surface area and should push more water, but a lot depends on the color of the boat, motor decals, water temp, time of day, and whether are not you are running down hill……..but seriously, the left one should be faster.

[Author]

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