Abstract: Stern drive assembly configured for utilization in an inboard/outboard power plant for a boat. The stern drive assembly includes a central rigid core that is configured at an upper portion to be coupled to the stern of a carrying boat. A lower portion of the core is designed to accept a boat-moving force generated by a water propulsion unit that is coupled thereto. A thin-walled housing is configured to be secured about a predominance of the centrally located rigid core. The housing has an outer surface that establishes an exterior of the stern drive assembly and an inner surface directed generally toward the central rigid core. A portion of an exterior surface of the central rigid core is configured to cooperate with a corresponding portion of the inner surface of the thin-walled housing. These two portions, when in cooperative orientation one with the other, form a functional feature for the stern drive assembly.

Abstract: A reversible stern drive system incorporates a continuous drive member looped about a first and second intermediate shaft and a propeller shaft to transmit rotational power from the intermediate shafts to the propeller shaft in either a first or second propeller rotational direction. Rotational direction of the propeller shaft is determined by selective coupling of either a first driven member to the first intermediate shaft by a first clutch or a second driven member to the second intermediate shaft by a second clutch. In a second embodiment of the invention, two separate continuous drive members are employed to drive two concentrically mounted propeller shafts. The first continuous drive member is looped about one of two sprockets on the first and second intermediate shafts and the first propeller shaft such that when one of the sprockets is coupled by a first clutch to the first intermediate shaft, the first propeller shaft rotates in a first propeller rotational direction.