In the beginning, inboard propeller shaft bushings were wood, machined
from the rock-hard tropical Lignum Vitae tree since that particular species of wood is very dense and self-lubricating. That is until the 1920s when a Californian mining engineer improvised a bearing using a chunk of common rubber steam hose pressed inside a sleeve. Necessity is the mother of invention. A pump bearing failed, it was the weekend, and all of the supply houses were closed. So the engineer fashioned an expedient bearing. And so it was that the modern day Cutless bearing, replete with flutes and naval bronze tubing, was born.
How a Cutless bearing works is as simple as the sea is salt. Notice the flutes, the grooves in the nitrile rubber tube, that lubricate the propeller shaft with water.Grit, particles and other abrasives that may wash into grooves are flushed away by seawater, protecting the shaft and prolonging bearing life.
Cutless bearing technology advanced significantly during the Second World War when during the battle for the Coral Sea reverberations from explosions in the water hardened the rubber in Cutless bearings. Battleship propeller shafts locked up solid. Battlewagons went dead in the water. Once back in drydock at Pearl Harbor rigid rubber was soon replaced by the more resilient nitrile rubber.
Some otherwise knowledgeable aficionados miss-spell Cutless as Cutlass. There is no "A" in cut-less. The product is protected by the US Patent and Trademark Office with trademark registration number: 77180957, owned by DuraMax Marine.