Exhaust emissions from four 2-stroke outboard motors were measured before and after being bubbled through water, and the constituents measured were: CO, CO2, NO, hydrocarbons, NOx, O2, and total aliphatic aldehydes and formaldehyde. The engines tested were a Chrysler 35 hp twin, a Mercury 65 hp in-line four, and OMC twins of 4 hp and 9.5 hp. The engines were operated on stationary test stands with power absorption by electric (eddy current) dynamometers driven from the propeller shafts. Pertinent operating data were recorded along with emissions, and mass emissions computed from data gathered during this project are used in conjunction with available sales and usage data to estimate national emissions impact. (Modified author abstract)