Nowadays, the challenge of reducing air pollutants, which passes through increasingly stringent regulations on emissions, is also central in the maritime sector. A possible solution to overcome these limits could be the introduction of alternative propulsion systems to classic diesel engines. In the present work, the performance of a Hybrid Propulsion System (HPS) in marine, consisting of an internal combustion engine and a Vanadium Redox Flow Battery (VRFB) allowing an independent power and capacity sizing, was analyzed. Specifically, through a dynamic modeling, a daily work cycle has been simulated on the basis of a real load request. The possibility of implementing a hybrid system independent from a ground-based charging system was evaluated, in relation to the analyzed work cycle, by identifying the size of the battery (70 kW/ 5.8 kWh) and its minimum charging power (23 kW) necessary for the autonomous operation. Together with the results of the dynamic analysis, experimental results obtained on a real VRFB prototype of the innovative concept design implemented are provided.