This paper researches combined marine propulsion systems and economic analysis of the mentioned. In the second chapter, each combined marine propulsion system is described individually, the working principle is being defined and main components of every combined marine propulsion system is being described. Furthermore, the paper also shows the advantages and disadvantages of the combined marine propulsion systems, in comparison to low speed diesel engines, depending on the type of vessel. In chapter three, there is an economic analysis of the combined marine propulsion systems shown. The main costs of the combined marine propulsion systems and short example of calculation of the mentioned is shown. The main advantages of using a specific combined marine propulsion system are elaborated and selection of combined marine propulsion system based on specific requirements of chosen ship using an analytical hierarchy process is described. As an example of the suitability of the specific combined marine propulsion system, the paper proposes solutions on two types of military ships and two types of commercial ships. This characteristics is defined by profitability, that is the ratio of gains and losses of using a specific combined marine propulsion system.