In an outboard motor shift control system to change the shift position by controlling the supply of current to an electric shift motor for driving a shift mechanism, a detent mechanism is equipped for constraining the operation of the shift mechanism and holding the shift position once the shift position has been established, and the supply of current to the shift motor is discontinued upon detection that the shift position has been established. This configuration makes it possible to minimize the power consumption of the shift motor and ensure secure holding of the established shift position.