An actuator for imparting steering movement to a tiller of a propulsion unit of a marine vessel, the actuator comprising: a housing; an output shaft reciprocatingly received by the housing; a motor disposed within the housing, the motor having a rotor and a stator, the rotor having a magnetic field and the stator having a magnetic field, rotation of the rotor causing the output shaft to translate axially relative to the rotor and causing the output shaft to reciprocate relative to the housing; a sensor (98a, 98b, 98c) for sensing a position of the rotor; characterized in that the actuator comprises: a steering control unit which energizes the stator to align the magnetic field of the stator with the magnetic field of the rotor, based on a position of the rotor sensed by the sensor (98a, 98b, 98c) for sensing the position of the rotor, to hold a position of the rotor, wherein the motor is at least a two-phase motor and the steering control unit energizes the stator by applying a PWM to at least one phase of the motor to generate a magnetic field that aligns with and holds the position of the rotor, wherein the steering control unit applies a minimum PWM to create a holding torque which counters a back driving torque, and wherein the steering control unit increases or decreases the minimum PWM applied in order to counter the back driving torque. a housing; an output shaft reciprocatingly received by the housing; a motor disposed within the housing, the motor having a rotor and a stator, the rotor having a magnetic field and the stator having a magnetic field, rotation of the rotor causing the output shaft to translate axially relative to the rotor and causing the output shaft to reciprocate relative to the housing; a sensor (98a, 98b, 98c) for sensing a position of the rotor; characterized in that the actuator comprises: a steering control unit which energizes the stator to align the magnetic field of the stator with the magnetic field of the rotor, based on a position of the rotor sensed by the sensor (98a, 98b, 98c) for sensing the position of the rotor, to hold a position of the rotor, wherein the motor is at least a two-phase motor and the steering control unit energizes the stator by applying a PWM to at least one phase of the motor to generate a magnetic field that aligns with and holds the position of the rotor, wherein the steering control unit applies a minimum PWM to create a holding torque which counters a back driving torque, and wherein the steering control unit increases or decreases the minimum PWM applied in order to counter the back driving torque. a steering control unit which energizes the stator to align the magnetic field of the stator with the magnetic field of the rotor, based on a position of the rotor sensed by the sensor (98a, 98b, 98c) for sensing the position of the rotor, to hold a position of the rotor, wherein the motor is at least a two-phase motor and the steering control unit energizes the stator by applying a PWM to at least one phase of the motor to generate a magnetic field that aligns with and holds the position of the rotor, wherein the steering control unit applies a minimum PWM to create a holding torque which counters a back driving torque, and wherein the steering control unit increases or decreases the minimum PWM applied in order to counter the back driving torque.