this may seem idiotic but I am in possesion of an older fs 91..my great wife bought it 8 years ago and due to illness i had to drop out of the hobby..but oh baby i am back but man so much has changed at least with power..I see planes requiring 90 size four strokes but i suspect that the 91 surpass for instance is more enging that its earlier counterpart..I am debating whether or not to just sell it here and step up to a 120 size as a better allround powerplant for a wider range of aircraft to fly..and if i sold it what is the value as its still brand spanking new in the box with papers etc..I guess i feel uncertain what kind of power an older os 4 stroke would have in a 60 size arf like extra or cap ..I want straight up if possible or at least strong static power to do snappy manuvers.. ok all you experrts tell me what ya think???

If it were me, I'd keep the engine (They're perfectly fine engines) and fly it on whatever 60 size plane you decide to get, then if it becomes boring, step up to a more powerful engine. That ol' 91 isn't really a slouch in my opinion.

Oh, and did I mention you can never have too many engines lying about?

I guess your probably right..heck I know it was very expensive back then..I suspect if i build light and put it on a 60 size plane it will do just fine..there is somuch to choose from..and incidentally I have a ys too and that has plenlty of pep and its a .53..no ya never have too many engines..aint this hobby great?/thanks I will stop whinning!!