Thanks for all the info. My plane has a fiberglass cowling that allows the engine to pultrude about an inch. I think overheating may be the problem. I will make vents that allow more air to exit the cowling. A larger prop sounds good and an easy fix. I will try a 17 by 5. I'm going to fly it tommorow. About experience, I have over a hundred hours flying gliders. Everyone I talked to says this plane is not a good trainer. I'm a bit nervous. Flying and landing are what gliders do all the time; it's taking off that has me woried. I have no idea how fast to go before I rotate.