I bought a conversion engine on RCU recently. It's got a brand new cylinder and piston. Ralph did the work, but I didn't buy it from him. It's very nice, and lighter than I expected. I think the only time it's been run since the new piston and cylinder is when Ralph set it up in his shop. It looks like a brand new engine.

I'm wondering about the prop size for it. I would think it should turn a 24-10 up in the 7000RPM range. I hate to buy a bunch of props to experiment. I've already been through that with the 50cc and 60cc engines. It gets expensive. VERY expensive.

The plane is an aerobatic model. Extra 330L with 90" wingspan. 1482 sq.in. It should weigh about 17--18 pounds RTF.

What would you buy? 23-10 or 24-10 or 25-10? I like NX, MSC or MenzS props.