Hello was hopping if someone can tell me if this is right. I bought two engines off a guy that said I was buying two Rossi R40 Aereos for $60 but I didn't fire them up until now. I was reading what the rpm are to show with an APC 10X6 and they say that I should be getting 17000 but when I turned this engine on they are hitting around 25500rpm. The sides don't say what size they are and it has a gray head on it.I'm scared that I will blow the engine with these reading. What I would like to Know is if the guy that sold me these engines knew what he had or am I doing something wrong. Second I bought these engines for a trainer because I got two for $60, I didn't buy the os46FX did I make a mistake.