This chart is provided as a guide to demonstrate what has worked for different sizes of engines in various aircraft. The extremes on either end of the scale may provide poor performance for your aircraft. Use these figures only as a guide for possible configurations. Begin by using the propeller diameter and pitch recommended by the engine manufacturer. If this information is not available, choose the diameter of propeller within the middle of the scale and experiment with the different pitches listed. This will provide a good performance propeller regardless of your aircraft set-up. On the other hand, if you have already discovered that turning a very small or a much larger diameter propeller on your engine has provided superior performance, continue using this diameter and experiment with the pitch to fine tune for optimum performance. A general rule is that planes with a lot of drag perform better with larger diameter propellers and a finer pitch. Airplanes with very little drag perform better with smaller diameter propellers and a coarser pitch. In unique situations, such as  “engine break-in”, it may be necessary to use a pitch that is not listed until the “break-in” period is complete. 

Go ahead and experiment with  pitch variations. Its easy and its free, unlike fixed pitch propellers! 

2 and 4 CYCLE ENGINES   
Note: 4 cycle engines use the larger diameter props

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