A hydraulic system for a marine vessel incorporates a single hydraulic pump that can be driven by either first or second motive devices, such as an internal combustion engine or an electric motor. Depending on the circumstances, the pressure required by the hydraulic system is provided by the pump when it is driven by either the first or second motive devices. As a result, only two motive devices can provide the necessary driving capacity for the hydraulic pump under all operating circumstances, including those when the engine is not running.