A method is for making a marine drive for propelling a marine vessel in water. The method includes providing a gearcase; installing a propeller shaft assembly that extends forwardly from the gearcase; coupling front and rear propellers to the propeller shaft assembly, forwardly of the gearcase, such that rotation of the propeller shaft assembly causes rotation of the front and rear propellers, respectively, which thereby propels the marine vessel in the water; and reducing deleterious effects of cavitation on the gearcase by the combination of forming the gearcase with a wide trailing end portion, in particular to maintain pressure alongside the gearcase, and configuring the front and rear propellers so that the front propeller absorbs more torque/thrust load than the rear propeller during said rotation.

A propeller (20) for a marine vessel (10), the propeller (20) comprising a plurality of propeller blades (24, 26). The propeller blades comprise a leading edge (30), a trailing edge (32) and an outer edge (34) located between the leading edge and the trailing edge. A transition from the leading edge to the outer edge occurs at a first transition point (36) and a transition from the outer edge to the trailing edge occurs at a second transition point (38). A straight line from the first transition point to the second transition point coincides with the outer edge (34) or is located at least partially outside the propeller blade. A smallest distance (D.sub.2) from the second transition point to the axis of rotation (A) is smaller than a smallest distance (D.sub.\) from the first transition point to the axis of rotation.

A propeller (20) for a marine vessel (10), the propeller (20) comprising a plurality of propeller blades (24, 26). The propeller blades comprise a leading edge (30), a trailing edge (32) and an outer edge (34) located between the leading edge and the trailing edge. A transition from the leading edge to the outer edge occurs at a first transition point (36) and a transition from the outer edge to the trailing edge occurs at a second transition point (38). A straight line from the first transition point to the second transition point coincides with the outer edge (34) or is located at least partially outside the propeller blade. A smallest distance (D.sub.2) from the second transition point to the axis of rotation (A) is smaller than a smallest distance (D.sub.\) from the first transition point to the axis of rotation.

A marine propeller having reduced noise characteristics, which has a hub having a central axis, one or more blades having blade length with a proximal end attached to the hub and a distal end extending radially outward from the hub, wherein the propeller has a diameter in between 360-400 mm, and wherein a combination of the diameter, pitch angle, skew angle, and number of blades of the propeller provides required thrust while generating low noise.

A marine propeller having reduced noise characteristics, which has a hub having a central axis, one or more blades having blade length with a proximal end attached to the hub and a distal end extending radially outward from the hub, wherein the propeller has a diameter in between 360-400 mm, and wherein a combination of the diameter, pitch angle, skew angle, and number of blades of the propeller provides required thrust while generating low noise.

A method is for making a marine drive for propelling a marine vessel in water. The method includes providing a gearcase; installing a propeller shaft assembly that extends forwardly from the gearcase; coupling front and rear propellers to the propeller shaft assembly, forwardly of the gearcase, such that rotation of the propeller shaft assembly causes rotation of the front and rear propellers, respectively, which thereby propels the marine vessel in the water; and reducing deleterious effects of cavitation on the gearcase by the combination of forming the gearcase with a wide trailing end portion, in particular to maintain pressure alongside the gearcase, and configuring the front and rear propellers so that the front propeller absorbs more torque/thrust load than the rear propeller during said rotation.

A method is for making a marine drive for propelling a marine vessel in water. The method includes providing a gearcase; installing a propeller shaft assembly that extends forwardly from the gearcase; coupling front and rear propellers to the propeller shaft assembly, forwardly of the gearcase, such that rotation of the propeller shaft assembly causes rotation of the front and rear propellers, respectively, which thereby propels the marine vessel in the water; and reducing deleterious effects of cavitation on the gearcase by the combination of forming the gearcase with a wide trailing end portion, in particular to maintain pressure alongside the gearcase, and configuring the front and rear propellers so that the front propeller absorbs more torque/thrust load than the rear propeller during said rotation.

A propeller, impeller or mixer comprising at least one blade, the blade having a suction surface and a pressure surface which extend from a leading edge to a trailing edge of the blade and a radially-outer tip region, wherein five to one hundred duct openings are provided extending through the at least one blade from the pressure surface to the suction surface, the duct openings being grouped in the tip region of the blade.

A propeller shield to selectively shield rotating blades of a propeller. The propeller shield may include a shield element for placement adjacent to the propeller blades. The shield element may include multiple gates configured to open in response to water flow generated by the propeller. The gates may be configured to open away from the propeller in response to a forward movement of the boat, and to close towards the propeller in response to cessation of the forward movement.

A propeller shield to selectively shield rotating blades of a propeller. The propeller shield may include a shield element for placement adjacent to the propeller blades. The shield element may include multiple gates configured to open in response to water flow generated by the propeller. The gates may be configured to open away from the propeller in response to a forward movement of the boat, and to close towards the propeller in response to cessation of the forward movement.