The paper presents examples of application of dual fuel marine engines based on the expertise of the largest marine engine manufacturers. The fueling systems of these engines have been presented as fueled with fuel gases in various combinations with liquid fuels. Examples of the application of dual fuel engines in vessels as well as variants of the powertrains have been shown. The results of own simulation research (Monte Carlo method) have also been presented related to the NOx emission from a variety of vessels operating in the area of the Bay of Gdansk proving that the use of engines fueled with fuel gas may indeed reduce the emission of NOx from marine vessels operating in this area.