Sailboat propellers have two requirements.
First, provide maneuvering power forward and reverse while not under sail power.
Second, have minimal drag while under sail.

   To achieve these requirements sailboat propellers have three general designs,
fixed, folding, and feathering.

    Fixed blade propellers have blades that do not move and typically have only two or three blades. The two blade propellers generally have less drag while under sail than the three blade propellers. These propellers are selected by cruisers and day sailors for lower drag (as compared to 4 blade Propellers), lower cost, high reliability and low maintenance. Typically these are the least expensive propellers. New start around $200

     Feathering propellers have blades that rotate to a position, when the motor is not running, to present minimal surface area for drag under sail. The pitch of many feathering propellers can be adjusted to the boat and motor by a having a diver adjust set screws that can change the pitch. Racers and cruisers like these propellers for lower drag under sail, better performance in reverse and mid range costs. These propellers need occasional mechanical maintenance.  New feathering propellers start around $800

    Folding propellers: The blades fold together when the motor is not running to present minimal surface area for drag under sail. When the motor is engaged the rotation opens the prop and holds the blades in a fixed pitch position. The pitch is not adjustable. These propellers are generally considered to have the best performance (lowest drag) under sail). These propellers may need occasional mechanical maintenance. New propellers start around $1000.

Prop Mounting
     If the propeller is in a close fitting aperture only fixed or feathering propellers can be used and the diameter of the propeller may be limited by the size of the aperture. The only propeller variables that can be altered to improve performance are pitch and number of blades. 
  
        aperture configuration                   

If the prop is in open water then all three propeller styles fixed, folding, and feathering can be used. The maximum propeller diameter can be determined by the dimension of the propeller shaft to the hull where the propeller will be mounted. Diameter, pitch, and number of blades can often be changed to match the motor and boat.


   open water configuration

Once the design of the propeller is selected then the processes of sizing and selection can begin.