The paper presenting the maintenance of modern marine engines using expert systems. The concept of modern marine engine, refers to an electronically controlled engine. The development of shipping and ships, it is our opinion of their size, strength and capabilities were developed and supporting things without which ship would not have the function. By this I mean the maintenance, modernization, automation of the ship and the like. Modernization and automation of the ship is actually a replacement of human labor machines. These machines must be functional and must perform tasks as instructed them to the man, and to be his worthy replacement. Expert systems are computer programs based on knowledge for some specialist areas. The area for which they are made, achieve quality and other expert conclusion, and help solve problems. In solving the problem of expert systems mainly rely on the integrated knowledge of experts, what corresponds to the knowledge that experts are efficient in solving problems primarily because of its accumulated knowledge. This paper describes the work and activities of the expert system ''CoCoS'' developed by company MAN-B & W for their engines, an expert system developed by the company MAPEX Wartsilla Sulzer AND SCADA system intended for control and monitoring of modern marine engine.