Seawater is the sole lubricant for your boat’s propeller shaft as it spins its way through life, turning thousands of rpm for hundreds upon hundreds of hours while you’re under way. The shaft is supported, typically, at its inboard end by the coupling that’s attached to the transmission; its other end is held in place by a fluted rubber tube referred to as a shaft or Cutless bearing. This bearing can be found, depending on the boat’s design, either within a shaft log that passes through the hull or in a strut some distance from the keel.
The Cutless bearing is usually made from a hard, rubberlike substance known as nitrile. Longitudinal flutes or valleys in the rubber tube are designed to improve water flow and to flush away any grit or other hard material that might wear on the shaft. The outer shell of the bearing may be made of either naval brass or a non-metallic composite, the latter for use with aluminium struts or stern tubes where corrosion could be a problem. Though durable, these bearings will wear out, and then they must be replaced to avoid annoying vibrations or, worse, shaft, log, or strut damage.
Found your dream Yacht in Greece? Drop me a message at steventruss1@aol.com I am back in Preveza mid November 2021.
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