SPECS: Displacement: .545 cu in (8.93cc)
Bore: .906" (23mm)
Stroke: .846" (21.5mm)
Practical RPM: 2,000-17,000
Power Output: 1.75 ps/16,000 RPM
Weight: 14.29oz (405g) w/o muffler
18.52oz (525g) w/ muffler
Recommended Props: 12x7-8, 13x6-7
I run my 55 with a APC 9X8 and a Jett muffler and it turns 16800 rpm in a CG Skylark 56. I've tried the recommended props (with the power box muffler) and it was a dog to me. Flying the 55 with a 11X5 would be a great combo if your into 3D or aerobatics. As far as premature wear due to high rpms, as long as you use a fuel with castor oil ( I add 3ozs to each gallon Powermaster or Omega) you will be OK: I've never wore out an airplane engine and I have 3 OS 77 ducted fans that are over 20 years old. I will admit to wearing out a couple boat motors but I was running 65-75% nitro in them.