Energy efficiency has a great importance to reduce both fuel consumption and greenhouse gas emissions, which are the most important focus points for researchers in maritime industry. Exergy analysis, which is widely used to design, analyze and evaluate thermal energy systems, plays an important role to increase energy efficiency. It reveals destruction of available energy in components and leads the researcher to achieve better engineering and systems. Advanced exergy analysis has the capability to reveal the interconnections among system components and improvement potential of inspected components and also the overall system. Steam cycle is used in ships as main or auxiliary power production means for a long time. Also, it is used to recover waste heat from high temperature exhaust gases. Organic rankine cycle (ORC) is an alternative energy recovery strategy to utilize relatively low temperature heat sources to produce power. Usage of ORC in marine power plants is relatively new field to explore. In this paper, a marine power plant with ORC is investigated. Energy and exergy analyses have been carried out to identify conditions and parameters that affect the efficient operation of the system. Then, a parametric study has been conducted to determine the optimum range of operation for power plant and ORC considering different load conditions. Finally, exergy destruction of each component is calculated to give further insight information about the potential of improvement for the efficient operation.