How to clean an anti-syphon valve on a yacht’s engine
Simple Boat Maintenance author Pat Manley show Yachting Monthly how to clean an anti-syphon valve on a yacht's engine
On sailing boats the exhaust pipe is swept up into a ‘swan neck’ to stop following waves flooding the exhaust when the engine isn’t running. Exhaust gas normally drives water up over the swan neck and out of the system, but of course if the engine isn’t running and seawater is entering the system, water will accumulate in the lowest section of the exhaust pipe.
Eventually there will be enough water to enter the exhaust manifold and run into any cylinder that has its exhaust valve open. Because water is incompressible it can shatter the piston or bend a connecting rod if you attempt to start the engine with water in the cylinder. Seawater entering working parts can also contaminate the oil and cause serious corrosion.
Salt crystal build-up can render the anti-syphon valve inoperable
Why it needs to be done?
An anti-syphon valve will eventually suffer from a build-up of salt crystals, blocking the air valve and causing it to become inoperative. An anti-syphon valve is fail-dangerous, in that you know neither if it’s working or if it has failed.
Where to find it?
If an anti-syphon valve is needed, the builder will probably have installed one.You might not know that it’s there as it needs to be fitted at least 150mm above the waterline, so it’s often out of sight.
To find out if you have one, look to see if the seawater supply pipe from the pump runs upwards above the engine and then returns down before going into the cooling system. You might, instead, find it doing the same thing, but after it leaves the engine prior to entering the exhaust.
The air bleed connection on Vetus’ anti-syphon valves rotate through 360°
Be aware that a short length of tube is sometimes led to the bilge from an anti- syphon valve to vent any dribbles of water that may occur. This is still an anti-syphon valve and needs to be serviced annually.
Cleaning process
Remove the top from the valve assembly, then remove the valve and clean it. Check that the vent pipe is clear by blowing through it. Carefully reassemble the unit.
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The post How to clean an anti-syphon valve on a yacht’s engine appeared first on Yachting Monthly.