To provide the engine mount structure for a compact planing boat capable of efficiently absorbing the vibration of an engine corresponding to the engine speed by structuring the natural frequency of the engine mount possible to be changed.

This engine mount structure for a compact planing boat is provided with a water jet pump to be driven by the engine. A hollow part 60, into which the fluid is led from outside, is formed inside the engine mount 6 for fitting the engine to a hull. A spring constant of the engine mount 6 is changed by adjusting the pressure of the fluid led into the hollow part 60 to absorb the vibration of the engine at the various engine speed.