The propeller shaft runs from the gearbox coupling through the stern gland and out to the propeller, supported at the stern by the cutless bearing, a rubber lined bearing lubricated by the water around it. In this video I remove the propeller shaft from Renko at the start of her restoration.

The shaft has to line up exactly with the engine and gearbox, or it vibrates. Renko comes back from Coast Marine with a machined propeller shaft flange, an internal spigot and better alignment.