Abstract: A ship includes a rudder and a propeller having a propeller shaft arranged adjacent a stern of the ship. A bottom of stern is made shallow to expose the propeller for a long distance and the rudder is arranged in a space defined by the bottom of the stern, the propeller shaft and a propeller post supporting the propeller shaft, thereby arranging the rudder nearer to a bow of the ship than the propeller. The propeller shaft comprises oil-water partition rings encircling the propeller shaft, and a bearing for the propeller shaft is formed with circular grooves which accommodate therein the oil-water partition rings and communicate with at least one oil-water separating pressurizing tank to form a water exhausting passage on an outer side of each the partition ring and an oil exhausting passage on an inner side of the partition ring.