Wärtsilä Marine Solutions commissioned this thesis to improve the testing procedure of marine parent engines, as well as to harmonise the way of working between two delivery centres. This was the initial aim, which exceeded the scope of Bachelor thesis. The new aim of the thesis is to provide background information through research for developing the guideline and tools. The work on the guideline and the tools is a follow-up task. The thesis research has been implemented through literature review and 17 specialist interviews. Interviews and other sensitive material has been removed from the public version. Environmental pollution is a widely recognized global problem. However, marine traffic environmental impact has been quite neglected...