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Propeller Definitions

Propeller Definitions


Matching each blades weight statically. This function takes out vibration allowing the prop to rotate smoothly

Blue Printing

Matching each propeller blade pitch quadrant from blade to blade.  This function is for each blade to mechanically move forward equally


Altering the propeller design. This function is to meet the boat/engine requirements for the ultimate performance gain. Used in racing, tournaments, fishing, water skiing, boat handling enhancement

Lab Finishing

Grinding the prop blade to create the most efficient thickness without losing the strength integrity. This function increases and enhances the performance of the propeller


This function is for appearance, help keep the prop clean, slow down the rust reaction, and smoothes out potential stress risers

Prop Repairs

Restores the propeller back to its original factory specifications

Leading Edge

The edge of the propeller nearest to the boat cuts through the water first, starting at the hub it extends to the blade tip

Blade Tip

This is the farthest point that a propeller extends from the center of the hub to the outer radius of the blade

Trailing Edge

The edge of the propeller farthest away from the boat where the water leaves the blade


The cup on a propeller is designed to help lock the propeller in the water to reduce slippage and prevent cavitation. The cupped area is located on the trailing edge of the blade starting approximately 1" from the hub extending out to the blade tip

Pushing Face

This is the face of the propeller blade away from the boat. Also called the Pitch Face which faces the pitch block when repairing

Negative Face

This is the face of the propeller blade toward the boat

Blade Root

The thickest area of a propeller where the blade and the hub are joint together


The center of the propeller that fits over the propeller shaft

Over Hub Exhaust

Exhaust gasses flow over the hub and blades

Thru Hub Exhaust

Exhaust gasses flow through a barrel of outer hub to prevent exhaust gasses from flowing over the blades of the propeller

Rubber Hub

Inner hub bushing made of hard rubber, molded to a splined spindle to protect the drive train when shifting

ACR/Diffuser Ring

The flared ring used on through hub exhaust propellers. The ACR/Diffuser ring prevents the exhaust gasses from backing up on the blades which produces cavitation on take-off


The introduction of air on the propeller blades resulting from running a damaged propeller, or from sucking air from the surface of the water. A cavitating propeller is actually slipping and produces less thrust


The theoretical travel of a propeller through a mass per revolution. EX: a 21" pitch propeller moves approximately 21" per revolution

Straight Pitch

The pitch is constant or the same from leading edge to the trailing edge of the propeller

Progressive Pitch

The pitch increases from the leading edge to the trailing edge. EX: Leading edge measures 17", trailing edge measures 19" pitch - this is a 2" progressive pitch

Variable Pitch

The pitch increases from the leading edge to the trailing edge, and from the hub to the outer tip


The angle of the propeller blade in correspondence with the propeller shaft

Foward Rake

Blades are angled toward the boat. Commonly used for inboard propellers and small outboard propellers

Aft Rake

Blades are angled back or away from the boat. Generally improves the ability of the propeller to operate in a cavatating or ventalating situation, such as the blades breaking the water surface.  Higher rake angles can better hold the water off into the air by centrfuge force

Parabolic Rake

The rake of the blades are progressive. Can be either concave or convex


The overall width of a propeller

Right Hand Rotation

The propeller turns clockwise on the shaft

Left Hand Rotation

The propeller turns counter-clockwise on the shaft

Performance Vent System (PVS)

A patented Mercury ventilation system, allows the boater to custom tune the venting of the propeller blades for maximum plane performance. On acceleration, exhaust is drawn out of the vent hole located behind each blade. When the next propeller blade strikes this aerated water, less force is required to push through this water allowing the engine RPM to rise more rapidly. Water flows over the vent holes once the boat is on plane sending exhaust through the exhaust passage. Varying the size of the exhaust holes engine RPM can be controlled, outboards perform better with venting and stern drives typically require less venting; if any at all.