Propeller - A device having blades attached to a central hub that is rotated to produce thrust to propel a vessel.

Diameter - A straight line passing through the center of a circle connecting two points on the circumference

Radius - A straight line joining the center of a circle to any part on the circumference.

See Also - Measuring the Diameter Identifying Propellers & Propeller Rotation

Pitch - the theoretical distance that a propeller moves forward in one revolution. Pitch

See Also - Identifying Propellers

Rake - the angle at which a blade differs from perpendicular. Rake

Blade Cup - A rolled edge on the trailing part of the propeller blade. Cup

Ventilation - Controlled air introduced around propeller blades to allow slippage and to improve throttle response. Ventilation

Cavitation - Uncontrolled air introduced by other elements which can cause loss of propeller grip through the water. Cavitation

Other terms -

Blade - The flattish working area of a propeller which cuts through water to propel a vessel.

Slippage - The deviation of a propeller from it's helical path through water.

Hub - The central position of a propeller through which the axis passes.

Leading edge - The edge of the propeller blade traveling forward which first contacts the water at a point closest to the boat.

Trailing edge - The edge of the propeller blade were water is leaving the blade at a point furthest from the boat.

Pitch Face - The side of the propeller blade facing to the stern of the vessel which is the working and measured side.

Diffuser Ring - Tapered ring fitted to the rear of thru propeller exhaust models which aids in prevention of exhaust gas interference with propeller blades at low speeds.

Propeller Bush - Rubber inserted hub molded to spline designed to cushion gear changing and to help prevent major engine / gearbox damage on impact.

Thru Prop Exhaust - The exhaust gases are directed through the hub of the propeller blades