Stricter rules and regulations about emissions for marine vessels and escalating fuel prices have motivated researchers and engineers to study further on improving fuel efficiency. Thus, it has become crucial to estimate the improvement potential and the sources of irreversibilities within energy systems. in this paper conventional and advanced exergy analyses are applied to a marine steam power plant to reveal insights which may help designers to make decisions on component renewal issues. The results of the study showed that the highest exergy destruction is within the boiler due to chemical reactions. Moreover, it has the highest avoidable exergy destruction. Pumps in the system contribute to the destruction in small percentages. Turbines have more importance compared to the heat exchangers. The findings for avoidable endogenous exergy destructions indicated that the improvement efforts should be focused essentially on boiler, turbines, condenser and pump equipment respectively, and that feed water heaters could be improved externally by improving other components. It is also concluded that the overall system has a 10% improvement potential of the exergy efficiency, of which almost three out of four is due to two components namely, boiler (6%), and low pressure turbine (1.3%), other components have smaller room for improvement. (C) 2018 Elsevier Ltd. All rights reserved.