Systems
Raw water pump repair and impeller service
The raw water pump pulls sea water through the cooling circuit, and it is the component most likely to leave you overheating offshore. I repair and replace raw water pumps, service impellers, and check the seals and bearings that fail before the impeller does.
The cheapest part on the engine stops the whole boat
A raw water pump impeller costs very little and takes an hour. An overheat caused by a failed one can warp a head. Worn pump bearings and a weeping seal give warning for weeks before the failure, and almost nobody looks.
What is included
- Impeller inspection and replacement
- Shed blade recovery from downstream components
- Pump seal and bearing replacement
- Cover plate and gasket service
- Pump housing wear assessment
- Cooling flow verification after service
How it works
Inspect
Impeller condition, blade count, housing wear, seal weep and bearing play all get checked together.
Repair
Rebuild or replace as condition dictates, and account for every impeller blade before the system is closed up.
Verify flow
Raw water discharge and operating temperature confirmed under load.
A failed marine raw water pump impeller can cause engine overheating within minutes, and any impeller replacement should account for all shed blades, because fragments that travel downstream lodge in the heat exchanger and restrict cooling flow.
Related systems work
Marine Generator Service
Service, repair and load testing for marine generators, the system that keeps air conditioning and power alive at anchor.
Marine Transmission Service
Gearbox service, fluid analysis, coupling and alignment work on marine transmissions and drive systems.
Cooling System Service
Raw water and closed loop cooling service, flushing and repair, the system that causes most marine diesel overheats.
Raw Water Pump Repair: common questions
How do I know the impeller is failing?
Reduced water at the exhaust, a gradual temperature rise, or a pump that weeps from the seal. Many owners find out only when the alarm sounds, which is why annual replacement is the sensible policy.
Should I carry a spare impeller?
Yes, along with the cover gasket and the tools to fit it. It is the single most useful spare on a marine diesel.
What happens to the blades that break off?
They travel downstream and lodge in the heat exchanger, which restricts flow and causes the next overheat. Every blade needs accounting for, and that means finding fragments rather than assuming they passed through.
Tell me what the engine is doing
Describe the symptom on the phone and most of the time the problem is narrowed before I arrive. Surveys are booked around your sea trial date.