ROD 8K2332 - Caterpillar

"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 is limited to 80% of the operation time. Expected usage is in the range of 4000 hours per year.
"C" Or Intermittent Rating
This application is for yachts with displacement hulls as well as ferrys with trips of less than one hour. This is also for fishing boats moving at higher speed out and back (such as lobster boats, crayfish boats, and tuna boats) and short trip coastal freighters where engine load and speed are cyclical. Full power (full throttle) operation is limited to 50% of the operation time. Expected usage of this rating is up to 2000 hours per year.
"D" Or Patrol Craft
This rating is for pleasure craft and yachts with semi-displacement hulls as well as patrol, customs, police boats, and some fire boats. This is also for bow/stern thrusters. Full power (full throttle) operation is limited to 10% of the operation time. Expected usage of this rating is up to 3000 hours per year, with the exception of the 3208 Engine. The 3208 Engine with a patrol craft rating is limited to 1000 hours per year.
"E" Or High Performance Rating
This rating is for pleasure craft with planning hulls as well as pilot, harbor patrol, and harbor master boats. Full power (full throttle) operation is limited to 5% of the operating time of the engine. Expected usage for this rating is up to 200 hours per year.