ORIGINAL: AstroDad
I tried a 12X7 and that seemed to be too much. I did not have a tach, but it seemed the revs were down and in a dive you could hear it rev up.
So?
I would expect an engine to speed up in a dive due to the engine not having to work as hard. I also don't like to over-rev engines. A good practical RPM for a 2-stroke is 11,000 - 11,500 RPM
And the OS 55AX manual even recommends a 12x7 to 12x8 or 13x6 to 13-7 prop.
By using an 11x6, you just might burn that thing up. Hell, I use an 11x7 on a 46!