Hifly, considering that the guys running the YS170-175 run the same props as I am, I'd have to say the OS33 puts out a little more HP than the YS's do. The extra HP however, is not required or necessary to fly F3A or masters.

The OS has very useful low end grunt just the same as the YS does, which has been an eye opener to me. I used to think no 2 stroke gas engine in this size could compete or compare to the low end of the YS 4 cycle. The OS has made that thinking obsolete. The fuel is avgas 100LL, but premium autogas works the same with a slight increase in power at the top, power which is completely unecessary for any schedule we fly. I opt for avgas because it is stable over time and doesn't stink... Avgas is purchased at any airport, usually around 2$ higher than autogas per gallon

I don't throw accolades like "impressive" or "stump puller" trippingly off the tongue; this engine simply delivers!!

You're here in NY....Do I know you? You might want to take a drive down and see for yourself