Darn it Doug, You got the pattern APC prop. They make two flavors. Pattern and Wide blade. Your correct in that the prop you own is for high rpm apps, the wide blade is to be used in our rpm range. You should gain quite a bit rpm, 300 and maybe as much as 800 over the Dynotrash prop, on the wide blade of course. That narrow blade one isnt going to make the thrust you want at the 4-strokes rpm range. BTW, the ryobi 4-stroke ignition coil has a buit in rev limiter. I'm not sure where its set to, someone else here might post it. So if you do find some high rpm that the motor spits and barks at, you know why. I love the APC 18-8 and 16-8 wide blade that I have. I've flown them on my ryobi and homelite conversions and the make tons of thrust over the DT props I have. I do like to use the DT props on scale planes but when the plane needs a power prop, APC wide blades are what you need.