Understanding the Parts of Your Boat’s Propeller

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Propellers are crucial for optimum performance on the water and to increase the lifespan of your boat engine (as well as the lifespan of the lake it’s used on!). The propeller is where the power of the boat meets the water, so it is important to have propellers with the right parts to achieve the boat’s full potential. Finding the propeller with the right parts is normally not an easy task for a boat builder as there are many variables to consider. You need to consider the boat design, weight, load distribution, the outboard running characteristics and by whom and where the boat will be used; all these influence the parts of a propeller and its potential impact on the environment. In this article you will learn about each of these parts and become more familiar with your boats inner workings.


The body is the support structure of the propeller. It provides an anchorage to the wings and houses the shaft. The common choice of materials for the body are either aluminium or possibly stainless steel. Aluminium provide good performance at a low cost while stainless steel propellers are more expensive than aluminium, however they are more durable and give a better performance.


The blades of the propeller can be looked at as the wings of the propellers and these are the parts that provide the thrust to move the boat. Most propellers have three or four blades. Three blades are typically more efficient but four blades generally provide a better grip on the water especially in tight turns or rough waters. After you decide which type of propeller to use, you need to determine the dimension of the blades. The main dimension is the diameter of the propeller, which is measured in inches at the tips of the blade. The other dimension is called the pitch, and it is the distance the blades will cover in one revolution. Lower pitch propellers will allow the outboard to build momentum quickly, which is helpful for heavy loads but they create less forward movement so you’re likely not to experience speeds as high as with the higher pitch.

The shaft

This is the rod that attaches the body of the propeller to the engine using nuts, seals and washers. It should be tightened using the instructions in the operator’s manual. The shaft should constantly be checked to ensure it is firm and straight. A bent shaft near the clutch can beat up the stuffing box and lead to the engine room flooding. Bending of the shaft normally occurs as a result of poor engine alignment, loose motor mounts or the propeller hitting something solid.

Shaft seals

This protects the motor from oil and grease by keeping the oil and grease on the rotating shaft while preventing the ingress of water into the motor. A common type of seal is the *PSS shaft seal. They are preferred for their durability, their ability to withstand high pressure and ability resist mineral acids, common organic fluids and solvents. They have a high speed capability, wide temperature range, low friction and come in standard and custom designs.

Understanding the parts of your boats propeller is much easier once you’ve read the information presented in the article above. You can now make a good choice as you also know some important attributes of the boat propeller parts or if you’re purchasing a boat you’ll be able to knowledgeably ask questions about the propeller. Go for a propeller made of stainless steel, with three blades and with PSS shaft seals. Also make sure the shaft is firm and straight and in good shape for your boat propeller to serve you longer.

Photo courtesy of the Flickr Creative Commons.

*This post was generously sponsored by Power Equipment.

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