It could also be a 40. Seeing that you have the steel prop hub, it's an older version. Remove the muffler and look into the exhaust port and count the rings. 1 ring=35cc, 2rings=40cc. My 40cc turns a Zinger 18X6-10 @ 7400rpm. Not bad for an old engine. For about $15 you can also add the points eliminator kit that will help reduce rfi. These are great running little engines and will last a long time. B&B Specialties has all the parts you could want for these engines.