A marine engine system (MES) should be evaluated by not only reliability (R) but also maintainability (M) and manning index (MI), because this system can be recognised as a typical man-machine system. In 1977 at the first ICMES Conference in Paris one of the authors presented a total evaluation of the MES with the three indices, R, M, MI, proving the human ability of detecting faults and defects in this system. This paper describes how the MES has developed from the point of view of the above three indices during the past 30 years in Japan and its problems in the future, and arrives at the following conclusions : the reliability of the MES has developed due to quality control (QC) ; the maintainability of the MES has improved due to education and training ; the manning index of the MES has improved due to Rand M ; the availability of the MES has kept constant due to the decreasing complement onboard, at the rate of one person per year approximately ; and two esimations having the three indices were shown by the SRIC 1990 Data Base in Japan, for the two kinds of subsystems in the developed MES.