18-6 to a 18-10 prop. They run best on straight FAI fuel(no nitro) The more nitro the fuel has the hotter they run. Thr tigre carb is adequate but if you can get your hands on an O.S 7D carb it will give at least 3 or 4 hundred more RPM and a little smoother throttle transition. I never had the need for a pump with mine as long as you don't get to carried away with the tank location. Hope this helped.