An outboard motor steering control system operates at starting of the engine to compare the output of the steering wheel angle sensor which indicates the turned angle of the steering wheel and the output of the rotation angle sensor which indicates the rotation angle of the swivel shaft, determines whether there is a phase difference in steering angle therebetween, responds to any phase difference found by, at the time the boat operator turns the steering wheel, controlling the operation of the actuator connected to the swivel shaft so as to eliminate the difference, and further operates to inform the boat operator of the difference. Owing to this configuration, the difference can be eliminated without causing the boat operator to experience an unnatural feel.