A small planing boat includes a multi-cylinder engine, and a propulsion unit driven by the engine for propelling a hull by drawing up and jetting out water. The engine can be configured to change the number of deactivated cylinders in a phased manner corresponding to an engine speed when the engine speed becomes a prescribed speed or more, and can include a memory for storing cylinder deactivation sequence schedules for determining sequences of cylinders that are deactivated and increasing the number of deactivated cylinders in a phased manner. An operation control device configured to deactivate the cylinders of the engine in a phased manner in accordance with the cylinder deactivation sequence schedules stored in the memory. The operation control device shifts the cylinder deactivation sequence schedules to be read out from the memory to another cylinder deactivation sequence schedule corresponding to an operational state of the engine.