Mr. Ghost, I am a Merco fan, I have about 8 of them, I missed out on the .61 Diesel though, Mr. Carlson keeps saying that he has a couple of used .61 Diesels and will clean one up and send it to me but so far it hasn't happened. My black .50 will fly all day turning a 12x6 Graupner at 8,500 rpm with nary a hiccup. People totally misunderstood how to run a Merco and tried to run them with 10x6s then were disappointed when it wouldn't happen. I am beginning to think it's not possible to wear one out. I do have a petrol .61 that may be the smoothest running engine I own.