The article compares between them three diesel-electric propulsion and power generation systems, characterized by a similar overall power but with diesel-generator sets very different in number and power; these systems are developed for the needs of an existing pleasure craft. In addition, each system configuration includes two versions, with diesel-generators operating at constant speed and other at variable one. Once defined the used diesel engines type, the characteristics of the six diesel-electric systems have been defined and optimized, by a genetic algorithm, in both design and off design ship speeds. The main performance, weight and cost of the generated systems, with both constant and variable speed diesel-generators, are compared between them and with the pleasure craft current mechanical propulsion system, for different vessel speeds. The comparison results are presented in graphical and tabular form and extensively commented.