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Water in the engine through the exhaust: who pays for hydrolock?
Short answer
If water has got into the engine through the exhaust,
the next start can hydrolock it and bend the con rods.
Who pays depends on the cause: an outside event, a handling error,
faulty installation or poor maintenance.
Most inboards have a wet exhaust. Raw cooling water is injected into the exhaust elbow, collects in the waterlock and is pushed out by exhaust pressure. The weak point is cranking: if the engine will not fire and you keep turning it over, the raw water pump keeps filling the waterlock but no exhaust pushes the water out, and it rises back into the cylinders. On engines below the waterline, sea water can siphon in through the cooling circuit if the anti-siphon valve is missing or stuck, and a steep following sea can push water up the exhaust. Once water is in the engine, the next start brings hydrolock: water will not compress, and con rods bend.
Who pays turns on the cause. An insurer will ask whether an outside event led to the damage, for example flooding after a grounding, or whether a handling error, faulty installation or lack of maintenance is behind it. Many hull policies exclude damage arising inside the engine from use, wear or poor installation, and machinery cover is a separate question. Our machinery cover, available from Basis Plus for machinery up to ten years old, names handling errors. What your own policy says decides, and a surveyor's report on the cause helps either way.
If the engine does not start after a few attempts, close the raw water seacock before cranking again and find the fault first. Have the anti-siphon valve checked at every service and the waterlock inspected for cracks. If the oil is milky or the engine turns over stiffly, do not try again: get an engineer to open it up, report the damage straight away and keep any removed parts for the surveyor. A second start with water in a cylinder often turns a repair into a new engine.
Worth remembering
Seacock shut, fault found
waterlock empty, engine intact
Kept on cranking
cylinders flooded, rods bent
When the engine will not start, the next attempt is the expensive one.
Questions
What owners ask us about this
How can I tell there is water in the engine?
Milky oil on the dipstick, an engine that turns over stiffly or not at all, and water from removed glow plugs or spark plugs. Stop trying to start it and call an engineer.
Does hull insurance pay for hydrolock?
It depends on the cause and the policy wording. An outside event is treated differently from a handling error, faulty installation or poor maintenance, and internal engine damage is often excluded. Read your own wording.
What does the anti-siphon valve do?
It lets air into the cooling line when the engine stops, breaking the siphon that could otherwise draw sea water into an engine fitted below the waterline. If it sticks it stops working, so it belongs on the service list.
Related
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Whether it is “Water in the engine through the exhaust: who pays for hydrolock?” or another question: send us your residence and the flag your boat flies. You will get a straight answer in one email; including a no, if that is the answer.
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