The economic performance of ship power plants is directly dependent on fuel consumption. Consumption is determined by the completeness of fuel combustion, which is influenced by many factors, one of which is the component composition. High molecular weight compounds, resins and asphaltenes contained in marine fuels are poorly flammable. They also form a coarse dispersed phase in the fuel, which complicates the process of hydrocarbon oxidation and leads to a decrease in its efficiency. It is known that ultrasonic influences increase the degree of fuels dispersion. The purpose of the work is to identify the regularities of ultrasound effect on the physicochemical indicators of distillate marine fuel of the DMA brand, which determine its operational properties: flammability, combustibility and pumpability. Experimental studies on the processing of marine fuel are carried out on ultrasonic devices LUK-0.125/50-O and Volna UZTA-0.4/22- 014 at a frequency of 50 and 22 kHz, respectively. For the theoretical substantiation of the observed effects, changes in the dispersed and structural-group composition of marine fuel are studied. The analysis of indicators in accordance with the regulatory documents is carried out. The greatest changes in all studied parameters are noted at an ultrasonic vibration frequency of 50 kHz. It is found that, in comparison with the initial sample, the kinematic viscosity decreases by 15 % after ultrasound exposure. The fuel density decreases by 0.002 kg / m3, the flash point of the fuel drops by 5 °C, and the cetane number shows a tendency to decrease by 2 points. The average particle size of the dispersed phase decreases by 12 %. An explanation for the improvement of the investigated fuel indicators on the basis of an increase in its degree of dispersion and redistribution of structural-group components is proposed. Ultrasonic treatment of marine fuel (50 kHz, 100 W, 43 s), carried out before feeding it to the engine on the fuel line in front of the filter and high-pressure pumps, can be used to improve the operational properties of the fuel and, consequently, reduce its consumption.