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.