105400-7231 ZEXEL 9 420 613 801 BOSCH GOVERNOR 9420613801 1054007231

Rating Definitions
The Caterpillar marine propulsion engine rating definitions are:* A - Continuous Duty-For heavy duty use with little load cycling (throttle operation up to 100 percent of total time) in oceangoing displacement hulls such as freighters, tugboats and bottom-drag trawlers, and deep river towboats. Expected usage is 4000 hours per year or more.* B - Medium Duty-For use with full throttle operation up to 80 percent of total operation time with the balance of time below rated rpm in midwater trawlers, purse seiners, crew and supply boats, ferry boats with trips longer than one hour, and towboats in rivers where locks, sandbars, curves or traffic dictate frequent slowing. Expected usage is 4000 hours per year, average, is typical, but could be higher.* C - Intermittent Duty-For use with full throttle operation up to 50 percent of total operation time with the balance of time below rated rpm in yachts with displacement hulls, as well as ferries with trips less than one hour, fish boats moving at higher speeds out and back (e.g., lobster, crayfish and tuna), and short trip coastal freighters where engine load and speed are cyclical. Expected usage of up to 3000 hours per year, average, is typical.* D - Patrol Craft-For use in patrol, customs, police and some fire boats. Also for bow/stern thrusters. Full throttle operation up to ten percent of total operation time with balance of time below rated rpm. Expected usage is less than 2000 hours per year.* E - High Performance-For use in pleasure craft with planing hulls, as well as for pilot, harbor patrol and harbor master boats with full throttle operation up to five percent of total operation time with balance of time below rated rpm. Expected usage is 200 to 300 hours per year. Some fish boats operate on duty cycles where D or E engine ratings apply.Time at full throttle is the cumulative time the engine is operated at full throttle load and speed during a work cycle, duty cycle, or voyage.These rating definitions dictate the selection of a rating for an application based on a load profile determined by time at various throttle settings or engine speeds. In general, an application requiring less time at full throttle, or lower engine rpm at reduced throttle operation, can utilize a higher rating.Application Guidelines
In selecting a rating for a specific application, the most important consideration is time spent at full throttle. Additionally, these rating definitions identify percent of time at full throttle and corresponding times below rated rpm. This rpm reduction lowers kW (horsepower) requirements as propeller demand follows a cubic speed/power curve.For example, an engine operating at 90 percent of rated speed would be loaded by a typical propeller to about 73 percent of rated power. Operating at recommended reduced speed controls the engine load at or below the continuous power level.As a general guideline, typical operating parameters for each rating level are summarized in the following chart. For more information, refer to your Caterpillar dealer and EDS