PURPOSE: To utilize governor thrust of a mechanical governor effectively by correcting fluctuation of a control rack position.

CONSTITUTION: An adjusting plate 23 is installed at a control rack 21 so that its position can be adjusted, and a rack pin 22 is projectingly-formed at an adjusting plate 23. The rack pin 22 is connected with the floating lever 34 of a centrifugal force governor 3. It is thus possible to adjust the position of the rack pin 22 to the control rack 21 by adjusting the position of the adjusting plate 23, correct characteristic dispersion of respective pumps, and adjust an opening in a fly weight 32 of the mechanical governor 3, utilizing the governor thrust effectively.