Injection Systems of Common Rail type are becoming widely used in marine engines. The aim of the research and development of these systems is to optimize the multi-injection process. The authors of the paper present the results of research on the fuel supply system of research common-rail marine medium-speed engine. The study was conducted for the nominal circulation engine speed. For the analysis were established three variants of fuel supply – a single dose, two-piece and three-piece The interdependence of measured injection parameters and their effect on engine operation have been presented in graphical form.