Anyone who has been following my other thread knows I have an O.S FP Max .40 engine from another plane that is underpowered for that airframe. Would it be advisable to put this engine in this aircraft even though the maximum recommended size is .32?

https://www.towerhobbies.com/cgi-bin...?&I=LXEWXD&P=0

52" of wing and right in the neighborhood of 4 pounds flying weight , In my opinion your O.S. .40 should fly it just fine

PS , this is coming from a guy who always goes slightly bigger on the suggested powerplant , within reason , of course

I put a Tower 40 in a Uproar which also had a 32 size recommendation limit and it flew great. IFRC the FP is a sport engine and not very powerful, much like the Tower 40.

I have an Evolution 40NX in my sonic and it flies quite fast. Make sure the fuel you use for the 40 FP has plenty of castor oil and try a 9X7 prop.

That is good to know. I usually run Wildcat Premium Plus which has 18% total oil. The prop that was on the plane when I bought it was an 11x6.

Are you sure about using a 9X7?
I have a 25FP and the instruction book recommends using a 8X6, 9X5 or 9X6 so using a 9X7 sounds a bit small. I'd be looking at something in the lines of a 10X5 or 6.
18% oil would be fine for your 40FP. In fact, that's what I run in my boats, 18% oil with 50% nitro, never had an oil related problem. Then again, my boat engines run at 25K+ RPM so more oil is a good thing

9X7 same load as 10X6 plus more ground clearance. Sleeve engines ( non ball bearing) require fuel with high amounts of castor oil, read the instructions if not they will overheat.