Caterpillar C7 and C9 marine service intervals

The Cat C7 and C9 marine engines (7.2L and 8.8L) are common in workboats and larger motoryachts. Oil and oil filter: every 250 hours, use Cat DEO or equivalent CJ-4 15W40. Fuel filter (primary Racor plus secondary Cat filter): every 500 hours, both simultaneously. Water separator: drain daily. Coolant: use Cat ELC (Extended Life Coolant, red), change every 6000 hours or 6 years, condition-check annually with a coolant test kit. Impeller: every 1000 hours or 2 years. Belt: every 500 hours. Zinc anodes on the heat exchanger: every 500 hours in salt water. Valve lash and injector adjustment: every 3000 hours. Injectors: replacement condition-based, typical life 8000-15000 hours in marine service. Aftercooler cleaning: every 2000 hours in salt water. The C7/C9 use electronic unit injectors (EUI), no user-serviceable timing adjustment, requires Cat ET (Electronic Technician) software for diagnostics.