A boat propulsion and steering system, comprising a pair of fully submerged rotors, a hull of a boat and means of motion generation of the fully submerged rotors, wherein: - The submerged rotors are each made by a propeller; - Each propeller comprises: o a horizontal Impeller with reverse blading; o a vertical rotation axis of adequate length to connect each horizontal impeller to means suitable for transmitting the force required for the rotation of the impeller; - a housing for each impeller obtained in the hull of the boat, delimited by o an upper flat surface totally closed; o a cylindrical lateral surface open towards the outer lower area of the boat-transom; o a flat lower surface, having a center and corresponding to the bottom surface of the hull and delimited by the boat centerline and a line within the point of rotation of the vertical axis of the impeller • the blades of said horizontal impeller are in reverse relationship, • said flat lower surface of the housing is totally open at the center and in a sector where the blading operates in agreement with the direction of movement of the boat, outer lateral zone, and said flat lower surface of the housing the system characterized in that: is closed in a sector where the blading rotates in the direction opposite to the direction of movement, lateral zone towards the boat center line. - The submerged rotors are each made by a propeller; - Each propeller comprises: o a horizontal Impeller with reverse blading; o a vertical rotation axis of adequate length to connect each horizontal impeller to means suitable for transmitting the force required for the rotation of the impeller; o a horizontal Impeller with reverse blading; o a vertical rotation axis of adequate length to connect each horizontal impeller to means suitable for transmitting the force required for the rotation of the impeller; - a housing for each impeller obtained in the hull of the boat, delimited by o an upper flat surface totally closed; o a cylindrical lateral surface open towards the outer lower area of the boat-transom; o a flat lower surface, having a center and corresponding to the bottom surface of the hull and delimited by the boat centerline and a line within the point of rotation of the vertical axis of the impeller • the blades of said horizontal impeller are in reverse relationship, • said flat lower surface of the housing is totally open at the center and in a sector where the blading operates in agreement with the direction of movement of the boat, outer lateral zone, and said flat lower surface of the housing the system characterized in that: is closed in a sector where the blading rotates in the direction opposite to the direction of movement, lateral zone towards the boat center line. o an upper flat surface totally closed; o a cylindrical lateral surface open towards the outer lower area of the boat-transom; o a flat lower surface, having a center and corresponding to the bottom surface of the hull and delimited by the boat centerline and a line within the point of rotation of the vertical axis of the impeller • the blades of said horizontal impeller are in reverse relationship, • said flat lower surface of the housing is totally open at the center and in a sector where the blading operates in agreement with the direction of movement of the boat, outer lateral zone, and said flat lower surface of the housing the system characterized in that: is closed in a sector where the blading rotates in the direction opposite to the direction of movement, lateral zone towards the boat center line. • the blades of said horizontal impeller are in reverse relationship, • said flat lower surface of the housing is totally open at the center and in a sector where the blading operates in agreement with the direction of movement of the boat, outer lateral zone, and said flat lower surface of the housing the system characterized in that: is closed in a sector where the blading rotates in the direction opposite to the direction of movement, lateral zone towards the boat center line.