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Winterising a boat after haul-out — the full preparation

The complete winterising checklist for after haul-out: engine, water systems, batteries, hull and frost protection.

The superyacht Lady Lau in Bonifacio

Winterising properly decides what state you find the boat in come spring — and mistakes can cost you an engine or burst systems. Frost is the greatest danger: freezing water expands and splits engine blocks, pumps, exchangers and pipes. The second enemy is damp, which leads to mould and corrosion. Good winterising means working systematically through every system to a checklist, ideally written down and ticked off.

Author: Maciej Baniewicz · Boat & Yard editorial team

Methodology: The material was prepared from the sources given and from practical service rules; the parameters have to be confirmed in the manual for the specific manufacturer or model.

The engine needs particular attention. Change the oil and filters (old oil contains acids that corrode during the lay-up) and flush the raw water cooling system and fill it with antifreeze, running it through the pump until it appears at the outlet. Fog the combustion chamber with preserving oil, stabilise the fuel or top up the biocide, and check the anodes. On engines with a closed circuit, check the concentration and condition of the coolant and its freezing point.

Water systems are frequent victims of frost. Empty the water tank and the calorifier, and drain the whole system — including pumps, filters, the water heater and the heads — or flush it with non-toxic antifreeze made for water systems (propylene glycol based, safer than ethylene). Remember the traps, seacocks and pipe runs at the lowest points, where water collects. Close the seacocks and, where possible, service them.

Batteries and electrics call for a decision: is the boat left connected to a charger, or completely disconnected? Batteries are best fully charged, and with no shore power they should be disconnected and topped up periodically, because a flat battery can freeze and be destroyed. Store lithium cells (LiFePO4) as the maker recommends, often partly charged and above freezing. Protect the terminals against corrosion and switch off any unnecessary circuits at the panel.

Prepare the hull and deck for the lay-up. Wash the bottom right after lifting out (growth comes off more easily while wet), assess the state of the antifouling and look for osmosis and damage. Clean the deck, check that the drains and scuppers are clear, and inspect and grease the moving hardware (blocks, winches). Sails, running rigging and deck electronics are best removed and stored somewhere dry. Secure the valves and hatches and check the hatches for tightness.

How the boat is stored matters a great deal. Ashore it must stand on solid supports correctly placed relative to the bulkheads, with the keel well supported; a tyre under the keel and even support prevent the hull deforming. A tarpaulin or winter tent protects against snow and UV, but must allow ventilation so that damp does not build up underneath — wrapping it tightly in plastic is the straight road to mould. Dry out the interior, open the lockers and lift the mattresses.

Safety and organisation: work with preserving fluids and fuel in ventilation and gloves, and dispose of propylene glycol responsibly too, despite its lower toxicity. Work carefully under a lifted boat and never trust a single support alone. It is worth drawing up a checklist and a list of jobs for the spring (refitting removed equipment, for example), so nothing is forgotten before launching. A written procedure gets better from year to year.

Material prices — products and options

Indicative prices in EUR (incl. VAT), as of July 2026. Products widely available in Europe; prices depend on the shop, the pack size and consumption. The links lead to example shops that ship across the EU. Dollar amounts are converted at 1 EUR = 1.1622 USD (ECB, 7 September 2026) and rounded — treat them as a rough guide, not a price in a US shop. Imperial values in brackets are conversions of the metric figure.

Antifreeze for water systems (propylene glycol)
Coolant / antifreeze for the engine
Oil and filters for the seasonal change
Preserving spray for the combustion chamber (fogging oil)
Fuel stabiliser and biocide
Charger / maintenance charger for the batteries
Moisture absorbers for the interior
Tarpaulin / winter tent with ventilation and supports

Price sources: svb24.com, garantboats.eu (Quicksilver). Prices are indicative and may vary depending on the shop and pack size.

Common questions

Which antifreeze goes into the fresh water system?

A non-toxic one based on propylene glycol — it is safer than the ethylene kind and approved for drinking water systems. Run it through the whole circuit: pumps, filters, calorifier, heads and traps, until it shows at the outlets.

Should the batteries stay on board over winter?

It depends on whether the boat has shore power. Left on charge it can keep its batteries; without power it is better to charge them fully, disconnect them and top them up periodically, because a flat lead-acid battery can freeze and be ruined. LiFePO4 cells are stored to the maker's instructions, usually part-charged and above freezing.

When should the bottom be washed after haul-out?

Straight after the boat comes out. Wet growth comes off many times more easily than dried-on growth, and a clean bottom lets you judge the state of the antifouling and spot osmotic blisters and damage right away.

Should the boat be wrapped tightly in plastic?

No. A tarpaulin or winter cover is there to keep off snow and UV, but it has to ventilate — sealing the boat in traps moisture underneath and leads straight to mould. Dry the interior, leave lockers open and lift the mattresses.

How should a boat be propped ashore?

On solid stands set against the bulkheads, with the keel well supported — even support and a tyre under the keel keep the hull from deforming. Work carefully under a boat on stands and never trust a single prop.

Recommended materials and sources