EMISSIONS CONTROL

A method of controlling emissions from a fixed-speed internal combustion engine includes injecting a controlled flow of air into the exhaust between a first catalyst bed adapted to reduce HC and NOx emissions, and a second catalyst bed adapted to reduce CO emissions, or in advance of a single catalyst bed. The flow of air is controlled to optimize the level of CO emissions, preferably as a function of engine load or temperature. In a marine engine-generator set, the flow of air is controlled as a function of generator load or temperature of the exhaust mixture entering the second catalyst bed, and seawater is injected into the exhaust stream downstream of the catalysts.