The temperature is dropping. If you don't drain your heater core and raw water pump correctly, you're looking at a $8,000 repair bill this spring.
The Threat: Expansion
Water expands by about 9% when it freezes. In a closed cooling system or an engine block, that expansion has nowhere to go but through the cast iron. A cracked block is almost always a total write-off for a marine engine.
The Checklist
- Drain the Block: Open the petcocks on both sides of the V8 block. Use a wire to clear sediment if water doesn't flow.
- Clear the Manifolds: Disconnect the lower hoses on your exhaust manifolds. These are often the first to crack.
- Raw Water Pump: Remove the impeller or drain the housing. Sitting water here will freeze and crack the housing.
- Heater Core: Often forgotten. Blow it out with compressed air or cycle antifreeze through it.
- Fog the Cylinders: Spray fogging oil into the intake while running to coat the cylinder walls and prevent corrosion.
Pro Tip: Don't just rely on "running antifreeze through". The thermostat might not open fully, leaving pockets of raw water in the block. Always drain manually first.
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