LAMP 9X4493 - Caterpillar

The Caterpillar four-level marine rating system has been changed to include a fifth classification. In the future, all marine engines will be rated "A" through "E".
These new rating categories should not be confused with the A-B-C-D Performance Categories of the Technical Information File (TIF) Performance Curve identification nomenclature.The rating definitions and application guidelines have been changed to add a new marine rating category which is called "patrol craft".
The future publications of the 0T charts will reflect the five-level marine engine rating. When making fuel power settings, always refer to the information plate on the engine. If changes are to be made to the engine's rating, be aware of the application. When a rating is selected for a specific application, the most important consideration is the time spent at full throttle. These new rating definitions identify the percent of time at full throttle. Time at full throttle is the percentage of time the engine is operated at the rated full load and speed during a work cycle, duty cycle, or voyage.
The definitions of the five-level marine propulsion engine ratings are as follows:
"A" Or Continuous Or Maximum Continuous Rating (MCR)
This rating is for heavy-duty service in ocean-going displacement hulls such as freighters, tugboats, bottom-drag trawlers, and deep river tow boats. The engine is operated at rated load and speed (full throttle) up to 100% of the time without interruption or load cycling. Expected usage is in the range of 4000 hours per year or more.
"B" Or Medium Duty
This rating is for mid-water trawlers, purse seiners, crew and supply boats, ferry boats with trips longer than one hour, and tow boats in rivers where either locks, sandbars, curves, or traffic dictate frequent slowing; and engine load and speed are constant with some cycling. Full power (full throttle) operation