Pitch is the theoretical distance a prop will move through a solid object in one revolution. Example a 13" prop will move 13" in one revolution. The other # is the diameter of the prop widest distance from blade edge to blade edge.
Pitch is the key number. The higher the number the harder it is to spin.but if it can make the rated rpm then it may be faster.
Lower pitch may improve hole shot and ability to stay on plane but may over rev if not watched carefully.
