The Environmental Protection Agency (EPA) published a final rule in the Federal Register that is designed to reduce exhaust emissions from diesel-powered recreational boats and simultaneously help the industry avoid a series of aftertreatment catalyst-based standards.
The rule would have required U.S.-flagged recreational marine diesel powered vessels with engines greater than 2000 kW to install catalyst aftertreatment systems. Because of language used in the original proposal, many yacht builders believed only yachts built or sold in the U.S. would be required to install the aftertreatment, including recreational yachts. A diesel catalyst system requires urea, which is not widely available nor is it necessarily suitable for storage on a recreational yacht.
Fortunately the rule was revised to exempt recreational yachts from Tier IV catalyst based standards.The National Marine Manufacturers Association worked to get this rule revised.