I rebuilt the 1978 Evinrude 70hp last September and it has been running great. Since the last engine I had was a 1960 model, Im not sure what to expect. I soaked and rebuilt the carbs and syncronized them per the book. The engine idles ok maybe some would say a little rough, never dies and starts easy hot or cold. It runs full throttle fine no missing popping etc.. How smooth should this engine be? Should it really purr or being 2 cycle is there some roughness. It has had this issue since I rebuit it. If i give it just a litte throttle running 10mph it will shake a little bit. It seems it only does this when slightly under load. Any ideas or is this nothing to worry about.