Well folks, I bought a 7-77 at a price I could not pass up. As most of you know I have the 9-90 and 7-70 I bought from Hobby King long before Horizon Hobby began distribution. The engines are serving me well with over 150 flights each! When I was writing/reviewing the instructions for the engines for Horizon I recommended a 22x12 prop for the 7-70 (7-77). This is a good prop for the 7-70 running at 5000 rpm, but still on the small side. I use the Xoar 22x10 three blade on my corsair which ground rpm is if I recall around 4000. I have been breaking in my new 7-77 with a 22x10 low load prop and staying below full throttle. I was seeing really high rpms over 6000! I decided to to try a too big prop I had reserved for my 9-90, a 24x12 on this engine. To my surprise this engine turned it at 5100 rpm! Using my true power calculator from Germany and the one from Astro Flight, neither of which give false high HP numbers, came to 3.4 PS and 3.7 HP respectively. Guys, these are strong performance numbers! 3.7 HP divided by 5.7 pounds = a power to weight ratio of .65 HP/ lbs! No, not a DA 50 performance but, this much power from a model radial is exceptional. I have said this before the carbs are shy on fuel delivery, even with large id short tubing and a high mounted tank. The 7-77 also works much better if the full throttle position is 3/4 open on the carb. -Tom