A marine vessel propulsion system includes one or more drive systems, each including an engine, an engine throttle, and a shiftable transmission. A control system for each drive system comprises a manually operable control lever assembly for electrically operating a servo assembly which mechanically operates the engine throttle and the transmission shifting clutches. The control lever assembly comprises a one-piece plastic support base which is adapted to pivotally support one or two identical one-piece plastic control levers. Components associated with a control lever are interchangeable and identical and include a potentiometer mechanically interconnected between the control lever and the base, a detent plate and a detent arm. The control lever assembly also comprises based-mounted components including a station selector switch, a mode selector switch, an electrical connector and a flexible circuit board for electrically connecting the potentiometer selector switches and electrical connector. The servo assembly comprises a plastic housing containing two identical servo units for mechanically operating the engine throttle and the transmission shifting clutches. Each servo unit comprises a support frame on which are mounted a reversible electric motor having a rotatable motor shaft, a rotatable link-drive shaft and a solenoid-operated clutch for connecting and disconnecting the motor shaft and the link-drive shaft. A potentiometer mechanically connected to the link-drive shaft is restrained from rotation by a clamp engaged with the motor housing.