How a boat spends the winter decides how its next season begins. A properly wintered boat starts on the first turn of the key in spring; a neglected one greets you with a dead battery bank, a musty saloon and a cooling system that quietly corroded for five months. The difference is a few disciplined days of work in autumn.
This guide walks through the wintering process step by step — from the haul-out decision to engine preservation, water systems, batteries and moisture control — and ends with a compact checklist you can print and take to the boat.
Haul-Out or Wintering Afloat?
Hauling out is the safer default. Ashore, the hull dries, osmosis risk drops, antifouling and anode work can be done at leisure, and there is zero chance of sinking at the berth. The trade-offs are storage cost and the stress that cradles and stands place on the hull if poorly positioned.
Wintering afloat suits well-maintained boats in protected marinas with mild winters, and it is kinder to some hull types. It demands more discipline, though: seacocks closed, bilge pumps and batteries checked regularly, mooring lines doubled and chafe-protected, and someone actually visiting the boat through the winter.
Engine Preservation
The engine is where wintering mistakes cost the most. Change the oil and filter before lay-up, not after — used oil contains acids and moisture that attack bearings all winter. Run the engine to temperature afterwards so fresh oil coats the internals.
Flush the raw-water side with fresh water, then check the coolant's antifreeze concentration on the closed circuit; tired coolant protects neither against frost nor corrosion. Remove the impeller so it does not take a set in the housing over five idle months, and store it labelled in the spring box.
Fill the fuel tank to minimise condensation and add a fuel stabilizer, running the engine briefly so treated fuel reaches the injection system. Diesel bug loves a half-empty tank over a damp winter.
Water Systems and Plumbing
Any water left in the system is a frost bomb waiting for the first hard night. Drain the fresh water tank, calorifier and all lines, then open the taps and leave them open. In colder regions, pump non-toxic antifreeze through the circuit until it appears at every outlet, including the deck shower.
Do not forget the less obvious water: empty and rinse the holding tank, winterise toilets according to the manufacturer's method, and drain air conditioning and deck wash circuits. The pipe you forget is always the one that splits.
Batteries and Electrics
A battery left flat over winter is usually a battery destroyed. Either take the batteries home to a cool dry place with an occasional top-up charge, or leave them aboard fully charged on a proper maintenance charger. Clean the terminals, grease them lightly and check electrolyte levels on wet cells.
Switch off every consumer at the panel and physically disconnect anything with a parasitic draw. The one exception is the bilge pump circuit on boats wintering afloat, which must stay live.
Interior, Moisture and Covers
Mildew is the smell of a badly wintered boat. Clean the interior thoroughly, empty the fridge and lockers, and prop open every cabin door, locker lid and floorboard so air can circulate. Take cushions and textiles home if you can, or stand them on edge.
Place moisture absorbers in each cabin or, on boats with shore power, run a small dehumidifier. Fit a breathable cover that sheds rain but does not seal the boat like a plastic bag — trapped condensation does more damage than the weather it was meant to keep out. Check the cover after the first storm, then monthly.
The Wintering Checklist
Work through this list in order: engine oil and filter changed; raw-water circuit flushed and impeller removed; coolant antifreeze checked; fuel tank filled and stabilizer added; fresh water system drained or filled with non-toxic antifreeze; holding tank emptied and toilets winterised; batteries charged and maintained or removed; seacocks closed (or serviced ashore); anodes inspected; interior cleaned, ventilated and fitted with moisture absorbers; cover fitted and lines checked.
Finally, write down everything you noticed during lay-up — the weeping stuffing box, the stiff seacock, the crazed hatch acrylic. Autumn notes are the cheapest work order you will ever write, because yards are quiet in winter and frantic in April.
Thinking Ahead to Spring
Recommissioning is wintering in reverse: refit the impeller, reconnect and test batteries, recommission the water system and flush it through, check belts, hoses and clamps, and run the engine on the dock before the first trip. If the autumn work was done properly, spring takes a weekend instead of a month.
If you would rather hand the whole process over, BALTA Yacht offers complete wintering and spring recommissioning service — engine preservation, systems winterisation and lay-up checks done once, properly, and documented.