In an apparatus for controlling operation of an outboard motor having an internal combustion engine to power a propeller, and a transmission selectively changeable in gear position to establish speeds including at least a first speed and a second speed and transmitting power of the engine to the propeller with a gear ratio determined by established speed, it is configured to determine whether the transmission is in a reverse position, and control operation of the transmission to change the gear position from the second speed to the first speed when the second speed is selected and the transmission is determined to be in the reverse position. With this, it becomes possible to prevent the thrust of the boat from decreasing.