This paper describes how four European navies have been able to work together for over twenty years in order to support their marine Tyne, Olympus and Spey gas turbines, used for surface ship propulsion, through two internationally agreed Memoranda of Understanding (MOUs). It shows how the MOUs came into existence, what their main aims are, how they are organised and how MOU business is conducted to achieve these aims. The final part of the paper discusses the merits of the existing MOUs and presents an insight into how they, and other MOUs currently under discussion, may develop in the future.