RE: GAS EQUIVALENTS TO GLOW ENGINES?
The correct Prop for a Super Tigre 2500 is an 18 x 6. The ST 3000's would turn a 18 x 8, and 18 x 10. Running a 20 x 6 prop would certainly be way beyond what a 2500 could pull efficiently, and throttle response would be slow. A moddern 30 cc gas engine would certainly be a fair replacement, and similar weight overall.