It kind of depends on how much money you want to spend. A Thunder tiger .42 or an OS 46LA both are inexpensive and will fly the plane quite well. I had one that had an OS 40FP on it and it was great. As a matter of fact 4 people learned how to fly with that plane and a 10 year old currently has it on floats. You are going to get opinions that you need a bigger expensive engine for this plane for future projects. Well All my future projects ended up with me buying engines for that specific project and the Eagle still has it's origional engine.