The National Marine Manufacturers Association is encouraging its boatbuilder members to submit comments to the U.S. Environmental Protection Agency on a new rule proposal that could negatively affect U.S.-based megayacht builders and large sportfishing boat manufacturers. The Clean Locomotive and Marine Diesel Rule was announced last Friday. It would set stringent emission standards and require the use of advanced after-treatment technology to reduce emissions on engines 2,000kW and larger. NMMA says the proposal sets the bar too low and establishes a bad precedent for the ruling to eventually extend, encompassing smaller, high-performance engines as well. The proposed standards intend to reduce emissions of diesel particulate matter and nitrogen oxide from these marine diesel engines through a three-part program: tightening emission standards for existing vessels when they are re-manufactured; setting near-term, engine-out emission standards (Tier 3) for newly-built marine diesel engines; and setting longer-term standards (Tier 4) for newly-built marine diesel engines that reflect the application of high-efficiency aftertreatment technology.