You must act

Boat owners who don’t bother to take precautions against frost may not be covered by their insurance policies, a Haven Knox-Johnston spokeswoman said. Last winter’s big freeze saw yachtsmen facing average repair bills for frost damaged engines of £7,000, she added.

In November 2010 temperatures fell to a freezing -10˚C in some parts of the country. Trapped freshwater in cooling systems or holding tanks will freeze at 0˚C, seawater at -4˚C. Catastrophic damage can be caused to any part of the boat which contains water; engines are particularly susceptible.

‘When water freezes it will expand by 9%. This causes fractures in the engine block or manifolds and risers. A common misconception is that a frost plug, or core plug, is designed to prevent damage from freezing. It rarely does,’ she said.

The spokeswoman said a reasonable boat owner should:

Drain down the engine and tanks before temperatures fall below freezing. Don’t forget the exhaust manifolds can also hold water, drain them too.
Follow the manufacturers guidelines in the owners hand book. Put the drains back in as soon as you’ve finished; If the engine has a closed circuit cooling system check the antifreeze is up to the correct strength. Drain down the heat exchanger, oil cooler or intercooler too.

If afloat ideally add antifreeze, at the very least drain down ensuring you replace the drains before you leave the boat. Add a heater in the lowest part of the engine room.Add an antifreeze mix of at least 50/50 ratio to water. This should protect to -30ºC, increasing antifreeze to 60% protects to about -45ºC. Don’t be tempted to use 100% antifreeze. Water is required for it to be effective.

One long term forecaster has predicted that the 2011-2012 winter “…will be exceptionally cold and snowy with well below average temperatures…it is therefore vital to start preparing now [by] raising awareness”.