Abstract: An engine unit having a throttle valve drive unit constructed so as to cause a throttle valve to rotate and stop at a desired angular position, characterized in that the throttle valve drive unit comprisesa synchronous motor for driving the throttle valve,a damping means for damping the rotation of the throttle valve,a voltage supply means for supplying d-c voltage to the synchronous motor, anda supply voltage control means for controlling the d-c voltage outputted by the voltage supply means;the throttle valve being adapted to stop at an angular position at which the rotational torque generated by the synchronous motor in accordance with the supply voltage of the supply voltage controlling means and the damping torque of the damping means are balanced.