Performance analysis of a power system utilizing waste heat energy from marine engines was conducted with Trifluoroethanol (TFEA) as the working fluid. The power system performance analysis was carried out using two methods. One involved the evaluation of the Rankine cycle thermal efficiency, and the other is the objective function for inlet and outlet temperature difference of waste heat gas. In the latter method, the maximum net power was obtained by minimizing the heat transfer area of the heat exchangers. The minimum value of the objective function was about 4 m2/kW when the inlet temperature of waste heat gas was 450 degrees Celsius. The marine engine power output was obtained from a performance analysis of a power system utilizing waste heat energy.