In collision-avoidance maneuvering in congested waters, an own ship is decelerated by astern power. The own ship is continuously navigated on a current target course with a propulsion propeller always rotated forward at the stern of the own ship. The astern power is generated as the propulsion of a propeller slipstream with rudder angles formed at a pair of right and left high-lift rudders disposed behind the propulsion propeller. In the decelerating maneuvering, the rudder angles formed at the high-lift rudders are controlled within a range from a rudder angle for applying a maximum propeller slipstream as the astern power to a rudder angle for eliminating the ahead power of the propeller slipstream, and the deceleration of the own ship is controlled by changing the astern power according to the rudder angles.

In collision-avoidance maneuvering in congested waters, an own ship is decelerated by astern power. The own ship is continuously navigated on a current target course with a propulsion propeller always rotated forward at the stern of the own ship. The astern power is generated as the propulsion of a propeller slipstream with rudder angles formed at a pair of right and left high-lift rudders disposed behind the propulsion propeller. In the decelerating maneuvering, the rudder angles formed at the high-lift rudders are controlled within a range from a rudder angle for applying a maximum propeller slipstream as the astern power to a rudder angle for eliminating the ahead power of the propeller slipstream, and the deceleration of the own ship is controlled by changing the astern power according to the rudder angles.

A steering device having two rudder plates vertically suspended at a distance from an outer edge of a propeller. The rudder plates are biaxially arranged and symmetrically rotate around a screw shaft within a propeller radius from a screw shaft center, on a propeller rotation plane, and are turned from aside the propeller to downstream of the propeller by rotation of the steering shafts, each of which is driven independently by two hydraulic driving mechanisms. The steering action of the steering device has two modes: the two-independent mode, where the plates rotate in the same direction, and the two-same direction modes, where the plates move in different directions. A method for steering the same to enhance a thrust flow by increase in a propeller rate is also provided.

A steering device in which a rudder plate is vertically suspended at a positive minimum distance from an outer edge of a propeller having a radius R from a steering shaft which is biaxially arranged and symmetrically rotates around a screw shaft within a propeller radius R from a screw shaft center, on a propeller rotation plane, and can be turned from aside of a propeller to a downstream of the propeller by rotation of the steering shafts, each of which is driven independently by two hydraulic driving mechanisms, and the steering device is characterized in that the steering action is divided into two modes: the two-independent mode and the two-same direction modes, and each mode is adapted as follows: at the time of ahead condition, each one of the two rudder plates is retained on both sides of a propeller parallel with a ship axis, and at the time of veering of the two-same direction mode, a rudder plate opposite to a veering direction turns 45 from aside of the propeller to the downstream of the propeller, and the other rudder plate turns 45 from aside of the propeller to the upstream of the propeller, and at the time of veering of the two-independent mode, the rudder plate opposite to a veering direction turns 45 from aside of the propeller to the downstream of the propeller, and simultaneously, the other rudder plate turns from aside of the propeller to the upstream of the propeller to take a rudder angle of 90 or more, to generate a thrust flow, and a method for steering the same to enhance a thrust flow by increase in a propeller rate.

A rudder mechanism for a marine vessel comprising of rudder that contains a first water flow surface essentially in planar form and an opposite second water flow surface essentially in planar form; a vertical rudder shaft that the rudder is linked by rotation around an axis that essentially extends perpendicular to the water flow surfaces of said rudder; and a drive mechanism for rotating the rudder around said axis. The rudder mechanism contains a rudder slot comprising the vertical rudder shaft and extending from the top section of the rudder towards the bottom section, wherein the rotatable link of the rudder and the vertical rudder shaft is essentially located close to the bottom of said rudder slot and is essentially linked to the vertical rudder shaft of said drive mechanism in such manner to exert force in the radial direction.

A rudder mechanism for a marine vessel comprising of rudder that contains a first water flow surface essentially in planar form and an opposite second water flow surface essentially in planar form; a vertical rudder shaft that the rudder is linked by rotation around an axis that essentially extends perpendicular to the water flow surfaces of said rudder; and a drive mechanism for rotating the rudder around said axis. The rudder mechanism contains a rudder slot comprising the vertical rudder shaft and extending from the top section of the rudder towards the bottom section, wherein the rotatable link of the rudder and the vertical rudder shaft is essentially located close to the bottom of said rudder slot and is essentially linked to the vertical rudder shaft of said drive mechanism in such manner to exert force in the radial direction.

A marine maneuvering system for maneuvering a vessel body includes a steering including a steering wheel, a manual operator on the steering to cause predetermined functions to the vessel body to be executed, and a controller configured or programmed to change the predetermined functions executed by an operation of the manual operator in accordance with maneuvering modes in which behaviors of the vessel body are mutually different.