The aim of the performed research was to develop of a diagnostic method of the flow section of a marine turbine combustion engine based on the level of delamination of its energy characteristics. The here adopted diagnostic model provides for a formulation of the evaluation of the technical conditions based on the measurements of the parameters of the thermodynamic medium in the characteristic control cross-sections of the flow section of the engine during a steady engine operation at nominal load. Based on the energy balancing of the individual impeller sets calculations were performed of their parameters in the form of a distribution of the stream of enthalpy along the flow section. This constituted the basis for the diagnostic conclusions on the overall technical condition of the engine at the same time enabling the identification of the spots of greatest energy losses.