Reading a size marking.
In a marking such as 13 1/4 × 17, the first number is diameter and the second is pitch, both in inches. The same diameter can be written as 13.25. The SEAPOW finder accepts decimal and common fractional size searches.
Diameter and pitch describe different things.
Diameter is the diameter of the circle swept by the blade tips. Pitch describes the theoretical forward travel in one revolution without slip. Actual boat movement depends on slip and operating conditions.
Rotation is a separate specification.
RH and LH identify right-hand and left-hand rotation. Confirm the rotation required by the engine installation; do not select it from a product photograph alone.
A matching size is only a starting point.
Two propellers with the same dimensions may differ in spline, hub, blades, gearcase application and rotation. Use those specifications together with the exact engine model and year.
Changing a size.
Pitch changes can affect engine loading and operating RPM. Confirm the permitted operating range and suitable propeller choice with the engine or boat manufacturer, or a qualified marine technician.
Use the propeller finder ↗