Hybrid propulsion systems with DC distribution for marine applications are attracting interest due to the critical demands to reduce the fuel consumption and emissions of conventional marine vessels. To enhance the potential of these hybrid systems, it is essential to develop an energy management strategy (EMS) to distribute the required power properly between various components of the hybrid system. This paper therefore aims to develop an efficient EMS for DC hybrid electric marine vessels (HEMVs). The proposed EMS builds a set of operation rules which are based on the system states including power demands, engine states and battery performances to minimize the total consumed energy of the system and thus increase the power efficiency. The performance of the proposed EMS has been validated through numerical simulations.\ud