SEAL-RING 1515257 - Caterpillar

Operating an engine above the engine's rating will reduce the service life of the engine before overhaul.
The following Table 1 defines the ratings for 3500 Marine Engine.
Table 1
Marine Engine Rating Definitions
Rating Typical Application Typical Hours of Use Per Year Typical Load Factor Time That Is Allowed At Rated Power Interruption or Load Cycling
Unrestricted Continuous “A” Bottom drag trawlers(1)
Deep river towboats(1)
Freighters(1)
Tugs(1) 5000 to 8000 80 to 100% 100% No
Heavy Duty “B” Crew boats
Ferries(2)
Mid-water trawlers
Purse seiners
Supply boats
Towboats(2) 3000 to 5000 40 to 80% 80% Some load cycling
Maximum Continuous“C” Coastal freighters (short trip)
Ferries
Fishing boats(3)
Tugs (harbor)
Offshore service
Yachts (displacement hull vessels) 2000 to 4000 20 to 80% 50% Cyclical engine load and rpm
Intermittent Duty“D” Off-shore patrol boats(4)
Customs(4)
Police(4)
Fire boats(4)
Cruising yachts (planing hull vessels)
Fast passenger vessels(4)
Fishing boats(3)
Bow/stern thrusters 1000 to 3000 Up to 50% 16% Some full engine load and rpm
High Performance “E” Harbor patrol(4)
Harbor master(4)
Fishing boats(3)
Pilot boats(4)
Fast yachts(4)
Pleasure craft(4) 250 to 1000 Up to 30% 8% Minimal full engine load and rpm
(1) Heavy-duty service
(2) The vessel must be slowed frequently for locks, sandbars and curves.
(3) Typically, examples of these boats move fast for cruising from the harbor and to the harbor: crayfish boats, lobster boats and tuna boats
(4) Typically, examples of these boats move fast for cruising from the harbor and to the harbor with low load factors.