A boat includes a planing hull, a propeller, a main rudder, and a pair of flanking rudders. The planing hull has port and starboard sides, a transom, a hull bottom, and a centerline running down the middle of the boat, halfway between the port and starboard sides. The propeller is positioned forward of the transom and beneath the hull bottom. The main rudder is positioned aft of the propeller. The main rudder has a rotation axis about which the main rudder rotates. The flanking rudders are positioned forward of the propeller. One of the flanking rudders is positioned on the port side of the centerline, and the other flanking rudder is positioned on the starboard side of the centerline.

A boat includes a planing hull, a propeller, a main rudder, and a pair of flanking rudders. The planing hull has port and starboard sides, a transom, a hull bottom, and a centerline running down the middle of the boat, halfway between the port and starboard sides. The propeller is positioned forward of the transom and beneath the hull bottom. The main rudder is positioned aft of the propeller. The main rudder has a rotation axis about which the main rudder rotates. The flanking rudders are positioned forward of the propeller. One of the flanking rudders is positioned on the port side of the centerline, and the other flanking rudder is positioned on the starboard side of the centerline.

A boat includes a planing hull, a propeller, a main rudder, and a pair of flanking rudders. The planing hull has port and starboard sides, a transom, a hull bottom, and a centerline running down the middle of the boat, halfway between the port and starboard sides. The propeller is positioned forward of the transom and beneath the hull bottom. The main rudder is positioned aft of the propeller. The main rudder has a rotation axis about which the main rudder rotates. The flanking rudders are positioned forward of the propeller. One of the flanking rudders is positioned on the port side of the centerline, and the other flanking rudder is positioned on the starboard side of the centerline.

To provide a gate rudder capable of reducing energy consumption during a voyage of a ship. A gate rudder including a pair of rudders including a left rudder and a right rudder disposed left and right, respectively, of a propeller at a stern, wherein each of the rudders includes a first rudder portion extending in a horizontal direction and a second rudder portion linearly extending in a vertical direction in rear view, wherein a rudder chord length of the second rudder portion in a front-rear direction is 40 to 100% of a diameter of the propeller, wherein the propeller is provided within a range of 15 to 65% of the rudder chord length from a front edge of the second rudder portion in side view, and wherein a rudder shaft that drives each of the rudders is provided at a position within a range of 30 to 50% of the rudder chord length from the front edge of the second rudder portion in side view.