PURPOSE: To largely reduce generation quantity of smoke in increasing an engine load or an engine output of a turbo diesel engine, and to restrict environmental pollution caused by smoke.

CONSTITUTION: For improving at least either of dynamic characteristics and output increase characteristics of a boost diesel engine for driving a variable pitch propeller, the pitch of the variable pitch propeller is first decreased till a rotation speed of the diesel engine and the variable pitch propeller is increased to reach a new rotation speed desired. Fuel injection quantity and diesel engine output (L) are then increased for the first time, and the propeller pitch is increased simultaneously with that for maintaining a roughly constant rotation speed.