Jimmy Rogers


Caterpillar C-18 Marine Engine Maintenance Schedule


This is a general guideline for service intervals on a Caterpillar C-18 Engine for recreational use

The Caterpillar C-18 Acert Engine is an inline 6, 4 stroke diesel engine with a displacement of 18.1L.  It is seen in recreational marine applications from 1000hp to 1150hp on yachts ranging in size from 45ft to over 70ft.

For further details please see the link at the bottom of this article that will allow you to download the actual CAT C-18 maintenance manual.

Some of these services will coincide with one another to be done at the same time for convenience and to save the number to trips your mechanic will have to make to the boat.  These are items needed in addition to your regular inspections of the motors prior to use.

*Also be mindful that the transmissions and generator will require regular service, consult with the manufacturers of those systems as well.  Often the same tech can perform services on all of them at once.

There are 3 different types of intervals that CAT uses to measure whether or not a service is due:

  1. Hours of use logged on the motors
  2. Age of the motors
  3. Fuel burned by the motors

Initial 20 to 40 Hours

  • Inspect Engine Belts, tighten, adjust, replace as needed

Every 50 Hours

  • Check aftercooler condensate drain valve, clean as needed
  • Check sea water strainers, clean as needed
  • Check zinc rods, replace as needed


First 250 Hours or 3750 gal burned

  • Check and adjust as needed engine valve lash
  • Check engine valve rotators
  • Check and adjust as needed fuel injectors


Every 250 Hours, 1 Year or 3,750 gal burned

  • Check auxiliary water pump and impeller and replace as needed
  • Check battery electrolyte level and voltage
  • Check engine belts and adjust or replace as needed
  • Check coolant system levels and add additive as necessary
  • Obtain coolant system coolant samples
  • Check engine air filter and clean or replace as needed
  • Clean engine crankcase breather
  • Change engine oil and filters
  • Obtain oil samples
  • Replace RACOR fuel filters
  • Replace engine secondary fuel filters
  • Inspect all hoses and clamps and replace as necessary


Every 1000 Hours, 4 Years or 15,000 gal burned

  • Inspect aftercooler core, clean and bench test for proper function
  • Inspect heat exchanger, clean and repair as necessary
  • Inspect turbocharger, repair as necessary
  • Replace closed crankcase ventilation fumes disposal filter


Every 3000 Hours, 6 Years or 45,000 gal burned

  • Inspect aux. water pump bronze impeller, change as needed
  • Change cooling system coolant
  • Replace cooling system water temperature regulator
  • Inspect crankshaft vibration damper
  • Inspect engine mounts
  • Clean and inspect engine speed/timing sensor
  • Check and adjust as needed engine valve lash
  • Check engine valve rotators
  • Check and adjust as needed fuel injectors
  • Inspect starting motor, replace as needed
  • Inspect Alternators, replace as needed
  • Inspect oil cooler core, repair/replace as needed

See below the link to download the actual CAT C-18 Marine Maintenance Schedule

CAT C-18 Marine Maintenance Schedule


Jimmy Rogers

OneWater Yacht Group

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