Raw Water System Repair in Australia
The raw water system is everything between the sea and the exhaust: the skin fitting, seacock, strainer, hoses, the pump, the heat exchanger, the oil and gearbox coolers, and the exhaust injection point. It is the system that keeps your engine alive, and it is under continuous attack from corrosion, growth and whatever the water carries.
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The components, and what fails
Skin fitting and seacock. Corrode and seize. A seacock that will not close is a safety problem, not just a maintenance one — it means you cannot isolate a flooding hose. They should be exercised regularly and replaced when they stop turning freely.
Strainer. Blocks with weed, plastic, growth and silt. The single most common cause of a sudden overheat, and the easiest thing on the boat to check. A strainer with a corroded lid or perished seal also draws air, which stops the pump priming.
Hoses. Perish, soften and collapse internally. A hose that has gone soft on the suction side collapses under pump vacuum at high revs — so the engine cools fine at idle and overheats at speed.
Pump. The impeller is the wear item, but the shaft seal, bearing and housing wear too. A weeping pump seal leaves salt crystals — a useful early warning. → Impeller replacement
Coolers. Heat exchanger, engine oil cooler, gearbox oil cooler. All block, all corrode, and all can perforate. → Heat exchanger service
Exhaust injection point. → Exhaust elbow replacement
The diagnostic order that saves money
When an engine overheats, work from cheapest and most likely:
- Strainer and seacock — is water getting in at all?
- Impeller — is it pumping?
- Hoses — collapsing under suction at revs?
- Heat exchanger — flow good but temperature high?
- Thermostat
- Head gasket or perforated cooler — coolant contamination
Most workshops that start at the top of that list finish quickly. The expensive mistake is starting near the bottom.
What good maintenance looks like
- Check the strainer routinely — before every trip is not excessive
- Exercise seacocks so they do not seize
- Replace raw water hoses on age, not on failure; squeeze them for softness
- Keep a spare impeller and hose clamps aboard
- Watch for salt weep, which shows a slow leak before it becomes a fast one
What it costs
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Frequently asked questions
My engine is fine at idle but overheats at speed — why? Classic collapsing suction hose or partial restriction. At low flow the system copes; at high demand it cannot.
How often should I check the strainer? Before every trip is reasonable, and after any run through weed or debris. It is sixty seconds and it prevents the most common overheat on the water.
My seacock won’t close — how urgent is that? Urgent. A seacock that cannot be closed means a burst hose cannot be isolated, which is a flooding risk. Have it serviced or replaced.
What is the white crusty deposit around my pump? Dried salt from a slow leak — an early warning of a failing shaft seal. Cheaper to address now than after the bearing fails.