In earlier years, high speed steam propeller's had a pitch equal to the diameter and this was considered state of the requirements to harness the torque of steam engines
In todays world of brushless high current capable motors, such pitch to diameter ratio's have been exceeded to use the available torque
The example below.....
Prop 2blade 38mm x 1.4 pitch 35Amps speed 27kph. is actually 38mm diameter with a pitch ratio of 1.4
So the propeller is actually designated as 38x53.......or ~~53mm pitch............
Another way to consider this is the example propeller has a blade tip to tip cylindrical helical displacement of 53 mm when rotated through 360 degrees ...
Again this 53 mm has no direct bearing in any longitudinal movement of the vessel through the water, nor considers fluid displacement efficiencies etc....
Derek