How is a cutlass bearing typically cooled?

A cutlass bearing is primarily cooled using water. This is due to the functional design and operational environment of vessels that use cutlass bearings in their propulsion systems. These bearings are commonly located in the stern tube of a vessel where the shaft exits the hull. Since they often operate in an environment where extensive heat can be generated from friction during rotation, the introduction of water provides necessary cooling to maintain optimal operating temperatures.

Water not only helps to keep the bearing cool but also facilitates lubrication, which is essential for reducing wear and tear. The water acts as a lubricant that reduces friction between the shaft and the bearing, thereby prolonging the life of both components.

On the other hand, while options like oil and grease can also serve as lubricants, they are not typically used for cooling cutlass bearings in marine applications. Oil can be used in other types of bearings and machinery but may not penetrate as effectively in the necessary cooling fashion as water does in this specific application. Air, while it can cool in some conjunctions, is not effective in reducing friction or providing lubrication like water can in this context.