Emissions of two- and four-stroke outboard engines—I. Quantification of gases and VOC

The effects of outboard engines on water quality were analysed under the controlled conditions of a test stand equipped with an 800 1. water basin. Two- and four-stroke engines with different power outputs were run with different fuels, lubricating oils and a newly designed catalyst. The gaseous emissions (HC, NOx, CO) and VOC (formaldehyde and 14 major aromatic compounds) introduced by the exhaust into the water were quantitatively determined. The weighted emissions of HC and the introduction of VOC (benzene, toluene, xylenes, etc.) into the water were much higher for two-stroke than for four-stroke engines. Using ethanol instead of regular unleaded gasoline in a two-stroke engine essentially reduced the emission of aromatic compounds. Different lubricating oils had no significant effect on the gaseous emissions and introduction of VOC into the water. A new catalyst designed for two-stroke engines with a bypass and post-combustion essentially improved the emission of gases and VOC.