Thought you peeps might like to know another bit of prop research I've come across
Currently I'm running a very peachy Yammy 75, which came with a stock 13x19 K series ally, which has a few dings in it, so in the mean time I took it off to tidy it up as best I could, and fitted the motor with a stock 13x19 prop from my Honda BF90
At WOT the Yam gave only 4400 with the Honda prop, but when I fitted the Yammy one back on, it pulled 5000
I didn't measure speed .. the Yammie prop had faster pick up too.
So my conclusion and point is, that just because the size & pitches are the same ,it doesn't necessarily mean you'll get the result you're looking, were you to be changing props around, because the blade shape, design and cupping also has a clearly substantial effect. You can see the differences in the photos