When it comes to the EPA’s recent proposed delay to implementation of Tier 4 marine diesel engines ‘in certain high-speed commercial vessels,’ where you stand probably depends on where you sit.On September 6, the U.S. Environmental Protection agency (EPA) proposed to delay implementation of Tier 4 marine diesel engines “in certain high-speed commercial vessels.” Specifically; EPA mentions three kinds of vessels: lobster boats, pilot boats and a third, more open-ended reference to “other high-speed vessels,” possibly including hovercraft.