I bought a Hangar-9 P51 today at my local club swap meet, had an OS 91 installed in it. The original owner powered it up, and we tached it at just over 9000 RPM with a 15x6 prop. There were too many people wandering all over the airstrip, so we didn't get it in the air.

I came home and looked up the specs on the 2-stroke 91, and it mentions that it should turn a 13x8 at about 15000 RPM....

What should I realistically expect out of this motor if it were in strong condition? I think the 15 inch prop may be a bit much, but it shouldn't cost me 6000 RPM. This is the first 2-stroke I've owned in quite some time... is it OK to run the 30% heli fuel in it that I use in my 4-strokes?