A steering system for a marine vessel comprises a first propulsion unit, a second propulsion unit, and a third propulsion unit. There is a hydraulic actuator for imparting steering motion to the first propulsion unit and a hydraulic actuator for imparting steering motion to the second propulsion unit. A tie bar couples a tiller of the third propulsion unit to the hydraulic actuator of the first propulsion unit. A joystick is used to input user steering commands to the steering system. Movement of the joystick actuates the said hydraulic actuators to impart steering motion to the first propulsion unit and the second propulsion unit. The third propulsion unit is put in neutral when the joystick is used to input user steering commands.