Many companies no longer need to rely on periodic inspections to determine machinery condition but they can also retrieve information from computerised continuous monitoring systems. Through appropriate software and hardware installation, these systems can diagnose possible failures of the machinery and predict needed maintenance. This paper is examining the tuning of a vessels main engine running mode, by successfully applying the Taguchi optimisation method, in order to increase the quality of output power to the shaft, along with the reduction of NOx emissions. This technique involves statistical and approved industry methods by analysing and processing data from performance log of a long-term monitoring, during sea voyages of a double skin bulk carrier of 55,000 DWT during sea service.