Different brands of propellers can give you dramatically different performance. Blade shape, airfoil type and thickness, trueness of pitch, and the materials it's made of all affect how a propeller performs.

We once tested a variety of props that were all supposed to be the same diameter and pitch. We got very different full-throttle RPM measurements.

On an O.S. Max FS-120, a variety of 15 x 8 props got turned anywhere from 9,300 RPM to 10,100 RPM, all on the same engine.

If you're engine's running well, then the RPM you get is OK.

On our test stand, we've run an 18 x 10 APC prop on a SuperTigre S3000 and expect low to mid-8,000's with a SuperTigre muffler (not very restrictive). We'll be using Omega "Super-T" fuel on a well-broken-in engine.