Before you start
Gather the appropriate supplies and review the specific equipment manual.
- Engine and pump manuals
- Correct replacement impeller
- Gasket or O-ring
- Light
Step-by-step instructions
Check the service interval
Confirm the correct pump and impeller part numbers, inspection frequency and access method for your engine.
Isolate the cooling supply
Stop the engine, prevent accidental starting and close the correct intake seacock as instructed in the manual.
Open only when safe
Follow the pump-specific sequence and prepare to capture residual seawater without flooding the compartment.
Inspect blades and housing
Look for missing, hardened or cracked vanes, scoring and damaged seals; missing pieces may be lodged downstream.
Reassemble and verify cooling
Use the approved seal, reopen the intake and verify normal cooling-water exhaust flow after starting.
Safety note
Never open a seawater cooling circuit without knowing how to isolate it. An incorrect reassembly or closed seacock can destroy the engine.
Key takeaway
A failing impeller can damage an engine long before the temperature alarm becomes obvious.
Keep this job on your maintenance schedule
Save the topic as a maintenance task, choose a due date or engine-hour target, and record future service. Free and stored on your device.
Add to my maintenance plannerThis guide is for general education. Follow your equipment manufacturer’s instructions, current navigation guidance and applicable marine safety standards. When uncertain, use a qualified marine professional.