EPA’s Tier 4 Marine Diesel Engine Waiver
The U.S. Environmental Protection Agency may grant a conditional exemption under our domestic marine diesel engine regulations to allow boat builders to install exempt engines on a case-by-case basis where it can be demonstrated that commercially available Tier 4 marine engines are infeasible for certain compact high-speed vessels.
EPA created this Tier 4 waiver process in 2020 to address concerns from builders and operators of vessels such as lobster boats. See EPA’s 2020 regulation (pdf) (291 KB). Certain vessel design constraints can present challenges that may preclude the installation of modern Tier 4 engines.
Boat builders interested in obtaining a Tier 4 waiver under EPA’s existing marine engine regulations may submit an application to EPA following the process outlined in the document linked below. If approved, this waiver would allow a builder to install a new exempt engine with maximum power up to 1,000 kW that meets Tier 3 emission standards and other criteria.
EPA will review applications in accordance with the regulations at 40 CFR 1042.145(m). Engine suppliers may ship exempt engines after seeing evidence of EPA’s written approval.