In the article marine diesel engine monitoring systems has been discussed. Systems offered by well known engines and diagnostic equipment producers for example Norcontrol, Autronica, MAN B&W, ABB an system worked up by Technical Institute of Ship Maintenance of the Polish Naval Academy in Gdynia are presented. Monitoring systems can curry out a several functions, for example engine load and other engine parameter conditions monitoring engine parameters and processes monitoring in boundary states, wear process and high-level feedback functions of engine control and adjustment monitoring. New trends, simulated by the recent Optrand offers of long-life fiber-optic cylinder pressure sensors, are also presented in the article.