Off design conditions can have a severe impact on ship propulsion system behaviour. Resistance increase for instance leads to a higher engine loading, and can also easily lead to a decrease of cavitation inception speed with respect to calm water conditions. Wakefield variations due to ship motions, waves and manoeuvres also have effect on engine loading and on propeller cavitation. This dissertation discusses the model based development of a propulsion control system aiming at increased cavitation free time in operational conditions, while preventing engine overloading and keeping manoeuvring characteristics acceptable. The developed propulsion control system has been tested extensively in a simulation environment before full scale trials took place in February 2008 onboard a frigate of the Royal Netherlands Navy. Results in terms of full scale propulsion system behaviour are presented, including photos showing the propeller cavitation behaviour in operational conditions.