What Is a Cutlass Bearing?

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A cutlass bearing, also known as a shaft bearing, is a part of the mechanism of a propeller, often for a yacht or other seagoing vessel. Like all bearings they are used to control and smooth out the motion of a rotating shaft, in this case the propeller shaft.

Mechanism

The propeller shaft runs through the cutlass bearing inside the strut, which is the part protruding from the bottom of the hull. The bearing then holds the shaft steady as it spins to prevent damage.

Materials

A cutlass bearing bearing usually has a fluted neoprene or rubber lining and a brass casing; other models have a reinforced plastic casing. The fluting in the lining allows in water to cool the shaft and smooth its motion. This also cleans out any sand or grit which could eventually damage the mechanism.

Wear and Alignment

A cutlass shaft needs to be replaced every 5 to 10 years due to wear and tear. The shaft may also occasionally need to be realigned due to a collision in the water or wear in the mechanism or hull itself. If the shaft seems to be moving around or shuddering, this is probably a sign that it needs to be realigned or the bearing needs replacement.