I went out today and ran two different .61 engines that I have today and I got what I feel are very different results from two engines that I feel should have very similar performance. I first ran my Thunder Tiger Pro .61 that has a strap on Tatone pitts style muffler and used a master airscrew 3 blade 12x6 prop and I got a reading of 12,000rpm at full throttle and idle at 1,800rpm. I then wrote down this info and proceded to check out my other engine. The other engine is an OS 61FX with a slimline pitts muffler swinging a master airscrew 2 blade 12x6 prop. I got a reading of 11,400rpm at full throtle and 2,000rpm idle. I used Omega 15% fuel and both planes have an os #8 glow plug. A little histroy on the engines: The TT Pro .61 is well broke in but still in excellant condition and the OS .61 FX has had approximately 1 gallon of fuel ran through it. I honestly expected the .61FX to outperform the Pro.61 but that dont appear to be the case. I double checked my readings on both planes and yes I made sure that I clicked the 3 blade switch while taching the Pro.61 and the 2 blade switch on the .61FX on my tach. I even checked the calibration of my tach and all was fine. So any explinations? Also I checked the manufactures website for both engines and it says that the OS.61 Fx should produce 1.9HP @16,000rpm and that the TT pro .61 should produce 1.8 HP @13,000rpm. Also it appears that the pro .61 is performing great and that the OS 61FX is not according to that data? So any suggestions or ideas?

Thanks,
FUZZ