Dredging operations result in severe load changes, and the transient capability of natural gas-fuelled dual fuel engines in gas mode is not sufficient to cope with them. An energy storage system may compensate the difference depending on the system size and control strategy. Previously developed component models are adapted and expanded with natural gas combustion and a kinetic energy storage system. The dual fuel engine's performance and transient behaviour in gas mode is validated with data from a factory acceptance test. Both the effect of increasing the available engine power and increasing the power of the energy storage system are investigated. The simulation results show the trade-off between the transient capability and lower harmful emissions on one side, and the operational costs and system efficiency on the other side. Increasing the available engine power, enhances the drive system's transient capability by reducing load change experienced by each engine, but it also increases the fuel energy consumption and global warming potential. A kinetic energy storage system increases the average engine load and fuel energy consumption slightly. The higher engine load results in a lower methane slip and does, therefore, not result in a net increase of the global warming potential.