A marine propulsion system, supported by a strut, comprising an inner propeller shaft supporting a first propeller adjacent a trailing end thereof, and the inner propeller shaft is connected to the drive shaft for receiving and supplying a first portion of torque to the first propeller as well as transfer thrust, generated by the first propeller, along the inner propeller shaft back to the drive shaft. An outer propeller shaft supports a second propeller adjacent a trailing and thereof, and the outer propeller shaft surrounds the inner propeller shaft. A differential gear set receives a second portion of the torque and supplies the second portion to the outer propeller shaft so that the second propeller rotates in an opposite rotational direction to the first propeller. The thrust, generated by the first and the second propellers, is conveyed along either the inner or the outer propeller shafts, to the drive shaft.

A marine propulsion system, supported by a strut, comprising an inner propeller shaft supporting a first propeller adjacent a trailing end thereof, and the inner propeller shaft is connected to the drive shaft for receiving and supplying a first portion of torque to the first propeller as well as transfer thrust, generated by the first propeller, along the inner propeller shaft back to the drive shaft. An outer propeller shaft supports a second propeller adjacent a trailing and thereof, and the outer propeller shaft surrounds the inner propeller shaft. A differential gear set receives a second portion of the torque and supplies the second portion to the outer propeller shaft so that the second propeller rotates in an opposite rotational direction to the first propeller. The thrust, generated by the first and the second propellers, is conveyed along either the inner or the outer propeller shafts, to the drive shaft.

A bulkhead protector apparatus is described. The protector is configured to be mounted within a cavity of the sheetpile of a bulkhead in order to prevent waves, wake, and debris from reaching the top portion of the bulkhead, minimizing damage and prolonging the life of the bulkhead. An angled waterguard portion is disposed within the cavity, and is configured to deflect water down and away from the top of the bulkhead. The waterguard portion is mounted to a whaler of the bulkhead via a planar mount portion which is secured to the underside of the whaler of the bulkhead via stainless steel lag bolts.

A marine vessel has a hull with a bottom, a bow, a stern, and a propulsion arrangement including at least three propulsion units arranged at the stern of the marine vessel. The marine vessel has a base line and a centerline. The at least three propulsion units include a fixed centerline shaft propulsion unit with a shaft line and a propeller, and two turnable propulsion units with respective propellers and arranged at opposite sides of the fixed centerline shaft propulsion unit for steering of the marine vessel. For improving thrust efficiency, while maintaining optimal steering capability, the propeller of the fixed centerline shaft propulsion unit is arranged at a given distance aft of the stern of the marine vessel.

A marine vessel has a hull with a bottom, a bow, a stern, and a propulsion arrangement including at least three propulsion units arranged at the stern of the marine vessel. The marine vessel has a base line and a centerline. The at least three propulsion units include a fixed centerline shaft propulsion unit with a shaft line and a propeller, and two turnable propulsion units with respective propellers and arranged at opposite sides of the fixed centerline shaft propulsion unit for steering of the marine vessel. For improving thrust efficiency, while maintaining optimal steering capability, the propeller of the fixed centerline shaft propulsion unit is arranged at a given distance aft of the stern of the marine vessel.