Decoding Boat Propeller Terminology}

Decoding Boat Propeller Terminology

by

Todd Alan

For people with no previous association to boat propellers, the terms that are used when speaking about different types of propeller and propellers parts can seem quite confusing. This write up aims to increase your basic knowledge when it comes to dealing with boat props.

The parts of a boat prop: The normal boat propeller is made of either three or four blades which surround the hub. The hub, in turn, connects the blades of the propeller to the engines drive shaft. The blades are angled in the way that enables them to screw through water, thereby moving the boat ahead. The leading edge refers to the end of the blade that cuts through water, and the opposite side is referred to as the trailing edge.

The drive shafts teeth are referred to as splines, and these arent part of the propeller itself. A hubs design ensures that it fits into a drive shaft keeping in view the number of splines it has.

Various Features: A boat propeller is mainly classified depending on its diameter as well as pitch, and this is normally embossed on the hub in the form of two numbers (in inches). While the first refers to the propellers diameter, the second refers to its pitch. The diameter of a propeller is the distance from the end of the blade to the center of the hub. The pitch is used in referring to the distance that can theoretically be traveled by the propeller in one revolution. The reason that a pitch is referred to as a theoretical representation is because it can experience slips in different scenarios. Slip refers to the ratio between the actual distance traveled and the props pitch. The slip could be different under similar environments; for instance while a work boat might experience a 60% slip, a well kept private boat might experience a 15% slip in exactly the same weather conditions.

When it comes to a propellers rotation, it could be either right or left handed. While most commonly available props have right handed rotation, you could come across left handed rotational props when double engines are required to counter the torque of the motor.

A cupped blade is used to describe blades that have undergone special treatment wherein the trailing edges are curved. This is known to elevate performance levels in specific scenarios.

The rake is used to refer to the angle created by the blade and the hub. A negative rake would indicate that the props blades point forward and this is normally done for adding strength.

Before you start, it is important that you note down your engines specifications, such as make, horse power (HP), model, etc. and your existing props details like its material (steel, aluminum, etc), diameter, pitch, and number of blades. You can then comfortably embark upon your hunt for a new boat prop.

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Decoding Boat Propeller Terminology

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