PURPOSE: To obtain the most efficient engine operation by measuring the actual fuel consumption while keeping engine output constant, varying the mumber of revolution (r.p.m.) and propeller pitch, and by calculating the highest efficiency point for the specified ship speed with these data.

CONSTITUTION: A governor 20 and a propeller pitch 18 are controlled in such a manner that the output of a fuel rack position detector 23 which indicates the engine output is kept constant. The fuel consumption, is measured and the highest efficiency operation point for the specified ship speed is calculated by means of highest efficiency point calculating logic 12. The governor 20 and propeller pitch 18 should be controlled in such a manner that they coincide with thus calculated results, which give the highest efficiency operation.