Performance Propellers

Propeller Identification tips

Prop identification Tips.  Most manufacturers mark the propeller with prop diameter, pitch and shaft diameter. Some times the letter R or L for right or left hand will appear in the marking. A prop marked 12r7x1 would be a 12 inch diameter right hand 7 pitch prop for a 1” shaft. The markings will vary a bit between manufacturers the same prop could also be 127R1from a different manufacturer. Folding and feathering props may have individual blades marked in a similar fashion. By measuring the prop diameter and shaft diameter it is usually easy to figure out which is the pitch marking on the prop. 


     Prop diameter is easily measured. Just a tape measurement is all that is needed. Measure a two blade propeller from tip to tip. A three blade propeller will need to be measured from the center of the propeller to the tip of one blade and that dimension is doubled to get the diameter. Diameters are usually in inch increments.


Pitch is difficult to measure without special equipment.


            The USA (sae) shaft diameters are usually ”, 7/8”, 1”, 1 1/8, and 1 . The shaft can be measured on the boat just behind the prop or close to where the shaft exits the hull using a rule or caliper. Inside the boat the shaft can usually be measured at the stuffing box or coupler. 


        If the prop is not mounted on a shaft the shaft diameter cannot be directly measured because the propeller bore is tapered and changes sizes. However by measuring the smallest diameter in the bore of the propeller the shaft size can be determined from the chart below.

Shaft dia         smallest bore dia        keywidth

  0.750                         0.608             0.187

  0.875                         0.710             0.249

  1.000                         0.812             0.249

  1.125                         0.913             0.249

  1.250                         1.015             0.312



Right hand propellers

Right or left hand prop.

If you look at the prop as mounted on the boat and you are looking forward from the stern of the boat to the bow. If the edge of the prop is the farthest away from you is on the right the prop is right hand rotation. If the prop is off the boat and you are looking at the smallest bore diameter and the edge of the prop is the farthest away from you is on the right the prop is right hand rotation.     

3 blade left hand propeller

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Performance Propellers

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Homer, NY 13077                             Fax 607-749-4604