Owing to their simplicity and their ability to represent the engine behaviour sufficiently well, cycle mean value models have been used for investigations of the transient response of marine diesel engines as well as the development of engine control schemes. In the present paper, two cycle mean value approaches of different complexities applied to the modelling of a large two-stroke marine diesel engine are described. The first modelling approach is less detailed since only two differential equations are used to represent the engine crankshaft and turbocharger shaft dynamics, whereas the other engine operating parameters are calculated after the solution of a non-linear algebraic system. In the second approach, more comprehensive modelling is obtained by using four additional differential equations, so that the dynamics of engine scavenging and exhaust receivers are captured. Using both modelling approaches, cases of the engine transient operation are simulated and the derived results are presented. Then, by comparing the simulation results with previously published data, the advantages and drawbacks of each approach are discussed.