The relevance of the work lies in the fact that in the system for engine speed automatic regulation (ESAR) under study, the isodromic speed-regulating governor (SRG) responds differently to disturbances of various sizes due to the presence of two significant non-linearities. The first one is connected with the fact that the oil flow rate through the isodromic needle varies in a power-law dependence of the pressure difference. The second one is related to the deliberate overlap in the pilot valve ports, which prevents the regulator response to disturbances caused by the cyclic operation of the diesel engine and twisting of the camshaft when the pushers of the fuel pumps move to the cams. The purpose of the study is to develop recommendations for optimizing the ESAR of a marine diesel-generator plant with isodromic SRG, considering the disturbances of various magnitudes while ensuring compliance with the requirements of the Classification Society. It has been studied the ESAR of a marine diesel generator manufactured by Yanmar Co., Ltd. of model 6N18AL-UV with isodromic SRG Yanmar NZ61 of the large-capacity tanker "KORO SEA". Its technical supervision is carried out by the Classification Society, the "American Bureau of Shipping" (ABS).