What is Raw Water Strainer?
The raw water strainer is a clear or bronze housing with a removable basket filter located between the through-hull intake and the engine's raw water pump. It captures seaweed, shells, sand and other debris before they can damage the impeller or clog the heat exchanger.
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What it is
The raw water strainer is a clear or bronze housing with a removable basket filter located between the through-hull intake and the engine's raw water pump. It captures seaweed, shells, sand and other debris before they can damage the impeller or clog the heat exchanger. Some strainers have a clear top so you can see what's been caught without opening them. Always close the seacock before opening the strainer.
What it does
The strainer protects your cooling system by trapping debris in an easily accessible location where you can clean it out regularly. Without it, trash would clog narrow passages in the heat exchanger or destroy the impeller in the raw water pump, causing engine overheating. The clear lid lets you monitor for blockages and see what's being filtered from your local waters.
Why it matters
A clogged raw water strainer causes engine overheating, which can warp the cylinder head, blow head gaskets or crack engine blocks. Running without a clean strainer allows debris to damage the impeller (requiring replacement) or completely block heat exchanger tubes (which requires professional cleaning or replacement). Checking the strainer takes 30 seconds but prevents catastrophic cooling system failure that can destroy your engine.
General Maintenance
Check the strainer basket before every outing and clean it if you see debris. This is one of the most important pre-departure checks. In waters with heavy vegetation or during spawning seasons (when jellyfish and algae bloom), check it multiple times per day. Always shut the seacock before opening the strainer to prevent flooding. Keep spare gaskets aboard as they can deteriorate and cause leaks. Some cruising boats check their strainer daily as routine.
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