Today's designers of modern passenger ships seek to achieve the highest level of integration of ship systems. This ensures safety and reduces the scope of operation of the operator on the navigation bridge or control room. This paper describes vital marine systems and explains the logic of their management with the purpose of understanding their interaction in order to meet the operators‟ needs. The described systems include the automation system, diesel engines, the main switchboard and electrical propulsion. Manufacturers' procedures must be followed in order to properly use and maintain these systems, and to avoid damage to equipment and people. Writing marine instructions, describing in detail how the system works, would take a lot of time and resources, so finding correct information is left to the crew, which is extremely stressful considering the increasingly demanding tasks in the ships operation. The analysis of problems with electrical propulsion, which are addressed in the last chapter, increases the understanding of the structured data movement between the ship's systems.