ROLLER GP-TRACK-SINGLE FLANGE 1977637 - Caterpillar

The Caterpillar Marine Engine Rating System is an effective method for rating marine propulsion engines. This system provides broad capability in matching a rating to a particular application.The most important consideration when selecting a rating for a specific application is time spent at full throttle.Rating Definitions
The marine propulsion engine rating definitions are: A - For use with little load cycling in oceangoing displacement hulls such as freighters, tugboats and bottom-drag trawlers, and deep river towboats. B - For use 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. C - For use 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. D - For use in pleasure craft and yachts with semi displacement hulls, as well as patrol, customs, police and some fire boats. Also for bow/stern thrusters. E - For use in pleasure craft with planing hulls, as well as for pilot, harbor patrol and harbor master boats. 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 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.As a general guideline, typical reduced engine speeds for each rating level are summarized in the following chart: Fuel consumption at the suggested reduced rpm is at or near the engine's optimum fuel efficiency.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.Ratings Versus Applications
Ratings should be applied on the basis of vessel operation. It is incorrect to assign a rating to an application based only on the type of boat or hull design. Vessel descriptions such as workboat, fish boat, or ferry boat and hull design such as displacement or planing hull do not completely define the operating conditions of the vessel or the power demands from the engine. These descriptions could have more than one rating applied, depending upon how the vessel is operated.For example, the application of a vessel as a passenger ferry does not