The master Airscrew 20 X10 has a lot of mass to turn. I have a new BME 44 and I started with a Master Airscrew 20 X 10 also. I could only get 6400 RPM on the first tank. I took that prop of and tried a Top Flite Powerpoint 20 X 8 and it went up to 7000 RPM. I am going to try a Menz or a Master Airscrew Scimitar which looks like a Menz. Were you using the Scimitar prop or standard Master Airscrew? Your engine should get stronger as you burn more gas. I don't have much gas through mine yet, but that is what everyone is telling me.

Good Luck,

Chris