Abstract: A power steering system of an outboard motor to be mounted upon the body of a hull and including a steering bracket secured to the body of the hull, a swivel bracket rotatable about a body of the outboard motor and a pair of clamping brackets supporting the swivel bracket, comprises a manual steering unit for manually steering a steering element so as to operate the outboard motor, the manual steering unit including a link mechanism connected to the steering element and connected to the steering bracket, and a power unit operatively connected to the link mechanism of the manual steering unit. The power unit includes an electric motor for applying a steering assist force to the manual steering unit for reducing the steering load during steering operations through means of the link mechanism and also includes a mechanism for converting rotation of the electric motor into linear motion.