RE: Diesel 4 strokes
You do not want to flip the prop on a Diesel casually, they will start right in your hand on occasion. As to the mixture, you run them at peak/lean. The disadvantage to no compression adjustment is if trying to run a smaller prop the engine turns higher rpm for a given throttle opening reducing cylinder filling time and in turn reducing the compression pressure. That .80 above will barely run with a 13x6 on it but runs spot on perfect with the Bolly 13.5x8.