Raw-water side
- The raw-water pump impeller wears and can shed vanes. Cummins lists it on the marine schedule; boating guides say to carry a spare.
- Sacrificial zinc anodes protect the cooling system from corrosion and are inspected and replaced on schedule.
- Heat exchangers and aftercoolers foul over time and are cleaned at intervals.
If it runs hot
Check the raw-water intake, strainer and impeller first. See also our sister site's troubleshooting library linked from the maintenance hub.
Lay-up
Follow the Cummins storage steps for your engine, and protect the raw-water side from freezing where that applies. See storage.
Where this comes from
- Cummins: Marine engine maintenance (PDF)
- Cruising World: Replacing impellers and raw-water pumps
- Trans Atlantic Diesels: Marine engine overheating (PDF)
Last reviewed 2026-10-19. General information only: your owner's manual and service information come first.