This book contains a collection of peer-review scientific papers about marine engines' performance and emissions. These papers were carefully selected for the "Marine Engines Performance and Emissions" Special Issue of the Journal of Marine Science and Engineering . Recent advancements in engine technology have allowed designers to reduce emissions and improve performance. Nevertheless, further efforts are needed to comply with the ever increased emission legislations. This book was conceived for people interested in marine engines. This information concerning recent developments may be helpful to academics, researchers, and professionals engaged in the field of marine engineering.