Here is a Propeller Glossary from your friendly Propeller Expert so we all understand what each of the terms mean and how it will make our boats faster; should you ever want a real propeller for your boat please don’t hesitate to check out our Dan’s Discount Boat Propellers website or call us at 1-800-573-5533 M-F
Propeller
Has a center hub with attached blades placed so that each forms a spiral surface, it is used to propel a ship or boat. By its rotation in water, the propeller produces thrust by the blades, which creates forward motion.
Diameter
Is the distance from the center of the hub to the tip of the blade times two. It is also the distance across the circle that the propeller would make when rotating. The first number listed when describing a propeller is the diameter.
Pitch
Is the theoretical distance in inches, a propeller would travel during one revolution – assuming there is no “slippage” between the propeller blade and the water. The second number listed in the propeller description is the pitch.
Slip
is the difference between actual and theoretical travel of a propeller through the water. A properly matched propeller will move forward about 80 to 90 percent of the theoretical pitch.
Rotation
When viewed from the back of the boat, right-hand propellers rotate clockwise to move forward. Left-hand propellers rotate counter-clockwise to move forward.
Cup
Small curvature located on the trailing edge of the blade. A curved lip on the blades allows the boat propeller to get a better bite on the water. This results in less ventilation, slipping, and allows for a better take off.
Thru-hub exhaust Propellers
The exhaust gasses pass through the barrel part of the prop and out the back, without making contact with the blades. This gives a good clean water flow to the blades, resulting in good acceleration and hole shot.
Non thru-hub Exhaust Propellers
Are used on inboards using shaft drive propellers. Sterndrives and most outboards use through hub exhaust propellers.
Cavitation
Occurs when water vaporizes or boils due to the major reduction of pressure on the back of the propeller blade. Propellers can partially cavitate during normal operation, but excessive cavitation can result in physical damage to the propeller. The reasons for cavitation are inproper matching of propeller blade style to the motor, wrong pitch size and damage to the blade edges.
Ventilation
When surface air or exhaust gasses are sucked into the propeller blades, boat speed is greatly reduced and engine RPM’s climbs rapidly. This can result from hard tight cornering, too high of the motor mounting on the transom of the boat motor and by over trimming of the drive unit.
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