Many boats and some PWC are equipped with two-stroke engines. Conventional two-stroke engines produce roughly 14 times as much ozone-forming pollution as four-stroke engines. Also, 25–30% of the fuel and oil of two-stroke engines is discharged unburned with a portion lingering in the water column for a period of time.
Federal law requires marine engines to meet tough emission standards. Many new, clean-burning engines are already available; and the new technology provides easier starting, faster acceleration, quicker throttle response, improved fuel economy, and reduced fumes and noise.
Even though boat engines currently in use are not affected by the phase-in, the OSMB encourages retiring old engines and replacing them with newer, more efficient models.