Prop for my V

[tsubaki]

Originally Posted by garbubba

Tsubaki, I don't get how you went from a 19 pitch to a 17 & didn't increase RPM's or lose speed
Doug

Subtle changes in diameter with the same pitch prop will sometimes achieve your desired performance. Same is true in reverse by changing the pitch but not the diameter. Another facet is a cupped prop, it can make a world of difference.
A good case and point was on a boat my father had years ago. He kept working toward an ideal rpm by buying props then having them repitched, testing them then having the diameter ground. Got it down to two prop sizes, one would overturn the engine, the other would produce slightly less than desirable rpms. I can't remember the size but he ended up getting the same diameter and pitch prop (of one or the other) but cupped. The engine then did what he wanted.
Normally stainless and aluminum props of the same diameter and pitch don't perform the same. There is a relationship (I've forgotten) about matching a stainless props performance to an aluminum one. It seemed like the aluminum props had the ability to flex more, so needing a slightly larger diameter and less pitch to match the stainless props performance.
In my case it turned out that way.

[tsubaki]

Now, if I will ever get off my butt and get motivated, I'll try to see if I can get mine to the correct rpms with a prop I've had a couple of years.

[smkinnan]

well, used the 15x16 over the weekend.....what a piece of crap I still have no idea which way to go but I am definately putting the SS 14 1/2x21p back on. It outperforms the Aluminum 15x16 which question. I got the following numbers on the 16p prop over the weekend:

25mph - 3800rpm
32mph - 4200rpm

Couldn't seem to push much beyond 4400rpm so I didn't try. Absolutely sucked through the gas like nobodys business. I didn't realize that I have either a bad fuel guage or fuel sender until late on Sunday when I had to call Sea Tow to come and get my butt I am going to start a separate thread about how to test those two components to see which one is bad.

[tsubaki]

In a full bog down situation, that engine is capable of drawing 22 gallons per hour.

Is it possible the motor could be mounted too low on the transom?

Pictures and new thread.