A is the leading or cutting edge. The height at B is the trailing edge.
A propeller acts like a screw cutting through water as it turns. The amount of distance that a propeller can cut through in one full revolution is known as the pitch of the propeller. Pitch is usually marked in inches. This is the theoretical pitch. (Propellers are not as efficient as marked)
A propeller with a pitch of 16 " for every revolution (360 degrees) should travel forward 16", but due to its inefficiency when cutting through water (A propeller is not as efficient as it's pitch) a slip factor is usually added into any propeller size equation. Slip is measured in percentage. Ranges of slip from 12% to 20% is common for outboard motors depending on boat, motor applications. 18% seems average.
A loss of 1/4" Diameter could increase rpm by 200 revs.
Adding diameter will result in rpm loss.