CO_2-reduction is required in maritime industries as well as other industries. On the other hand, ship is the most energy-efficient transportation facility and it is not easy to reduce CO_2 emission from the ship. Therefore, combination of the multiple approaches for the CO_2-reduction in the ship appears promising. In this study, to achieve the energy saving in the ship, we aim to optimize the performance of the engine-propeller system, considering the ship motion. As the first step, a system simulator is developed. In the simulator, the behavior of the engine and the propeller is analyzed combining the ship hull motion. From the simulation results, it is clarified that the time scale of the fuel injection control influences the fuel consumption rate of the engine.