Boat Winterisation Checklist: How to Lay Up a Boat for Winter

Ashore or afloat: the decision that shapes the rest

Laying up ashore, on a cradle or props, lets the hull dry out and be inspected properly, and the boat can no longer take on water through a weeping seacock. It is the most protective option, and the yard will quote for the lift and the hard standing. Wintering afloat avoids the lift but leaves the boat exposed to gales, chafe and water ingress. Only the lines below change; the rest applies either way. Reread your insurance policy and berth or yard contract too: some set lay-up conditions.

• Ashore: cradle or props set up by the yard, a ventilated cover, the drain plug out so rainwater can't collect, the position of every seacock written down.
• Afloat: lines doubled up with chafe protection, plenty of fenders, the automatic bilge pump tested and powered (shore-power charger or a dedicated battery).
• Afloat: seacocks closed except the cockpit drains, which stay open; a phone number left with the marina office; a visit after every gale.

A lay-up timeline, from the last sail to spring

A lay-up starts before the lift-out: autumn is the busiest time for boatyard lifts, and some parts take time to arrive. Adjust the weeks to your yard and area.

• A few weeks before: book the lift; order filters, an impeller, anodes, oil and antifreeze; list what misbehaved during the season.
• Last trip out: run the engine up to temperature (oil drains best warm), note the hour meter, brim the diesel tank.
• Lift-out day: pressure-wash the bottom before the growth dries on.
• Through the winter: regular checks on the cover, damp and batteries (and the lines, if afloat), plus a visit after a storm or a hard frost.

Inboard diesel: the engine checklist

The engine is where a missed step costs most. The aims: no old oil or salt water inside, fuel that won't degrade, and no chance of starting it by mistake. A brimmed tank leaves less air, so less condensation. Pump diesel in the UK and the EU contains a share of biodiesel (FAME), which holds water, and the water at the bottom of the tank is where diesel bug grows and blocks filters. Used oil and filters go to the marina's waste facility or a recycling centre; The Green Blue, the RYA and British Marine's environmental programme, maps facilities for boaters (thegreenblue.org.uk, consulted 1 October 2026).

• Change the engine oil and oil filter while the engine is warm.
• Replace the fuel filters; drain any water from the separator.
• Tank brimmed: add a biocide if the separator has shown water or sludge.
• Flush the raw-water circuit with fresh water, then let the running engine draw non-toxic antifreeze through the strainer until it shows at the exhaust.
• Remove the raw-water pump impeller so its vanes don't take a set; note where it is stored.
• Check the level and frost protection of the coolant in the closed circuit.
• Change the gearbox or saildrive oil if it is due; inspect the saildrive diaphragm.
• Check the engine anodes and the exhaust elbow.
• Seal the air intake and the exhaust outlet, then hang an “Engine laid up: do not start” tag on the helm.

Outboards and petrol engines

Left upright, an outboard drains most of its cooling water, but salt stays in its passages. E10 has been the standard petrol grade in Great Britain since September 2021, and the government lists boats among the equipment that may not be compatible with it (gov.uk, “E10 petrol explained”, consulted 1 October 2026). If your engine isn't approved for E10, the same page points to E5, the 97+ octane grade sold at filling stations offering two grades. Ethanol blends also store poorly, so depending on the engine you either stabilise the fuel or run the carburettor dry.

• Flush with fresh water through flushing muffs, with the engine running.
• Drain the gearcase oil: milky oil means water is getting in, so a seal needs replacing before the season.
• Four-strokes: change the oil and oil filter.
• Grease the steering pivot; take the propeller off and check the shaft for fishing line.
• Store the engine upright and dry; empty or treat portable fuel tanks and keep them somewhere ventilated.

Water systems: any water left behind can freeze

Water trapped at a low point, inside a pump or behind a closed tap is enough to split a fitting when it freezes. The method never changes: drain, open, then protect whatever won't drain with a non-toxic, propylene-glycol antifreeze sold for marine or drinking-water systems. Never use toxic ethylene-glycol car antifreeze in anything that discharges overboard or carries drinking water. Watermakers and air conditioning have their own lay-up procedures: ask the installer.

• Fresh water: empty the tanks, open every tap (hot and cold, transom shower included), then run the pump dry.
• Calorifier: drain it, then isolate it on its bypass so antifreeze doesn't fill it.
• Low points: pump antifreeze through until it shows at every tap.
• Heads: flush with fresh water, then antifreeze; have the holding tank pumped out.
• Bilge: clean and dry the sump; check the pump strainer and float switch.
• Seacocks: exercise each one, check hoses and clips, record the position it is left in.

Batteries and electrics

Batteries left connected are drained by small permanent loads, and a discharged lead-acid battery freezes more easily than a charged one, so charge fully, then isolate. Ashore, take the batteries home to somewhere dry and frost-free, or leave them aboard on a maintenance charger if the yard provides power. Afloat, only the bilge pump stays powered. Lithium batteries are stored differently: check the state of charge recommended for long storage.

• Charge each bank fully, then turn off the isolators (except the bilge pump if afloat).
• Clean the terminals and protect them against corrosion.
• Write down each battery's age and condition to budget for replacements.
• Unplug the shore-power lead if nobody visits often; take portable electronics home.

Hull, deck, rig and sails

Lift-out is the year's best chance to see everything below the waterline. Wash the bottom straight away, on a wash-down area that collects the run-off, then inspect it dry. Antifouling can be done in autumn, while the hull is clean and dry, or in spring before relaunch, depending on the old coating, the yard's schedule and the new paint's maximum time before immersion, given on its data sheet. On deck, rain must never pool, and a cover must let air through or it traps the damp.

• Inspect the hull and gelcoat (blisters, knocks, cracks), anodes, propeller, shaft, stern gland or shaft seal, rudder and through-hulls; photograph and date every defect.
• Clear the deck and cockpit drains.
• Sailing yachts: take the sails off, rinse and dry them before folding; check bottle screws, clevis pins and split pins.
• Mast left up: check the rig tension and tie the halyards away from the mast.
• Cover: ventilated, taut, and not rubbing on the gelcoat.

Cabin, safety gear and paperwork

In a shut-up boat, damp does more harm than cold: cushions, bedding, cardboard and food come off, and air needs to move. Winter is also the time for safety equipment. A liferaft is serviced at a station approved by its maker, so book early; out-of-date flares are replaced. Expiry and service dates are printed on each item.

• Prop open lockers, the fridge and cupboards.
• Use moisture absorbers (or a dehumidifier, if the yard allows) and keep vents open.
• Record every date in one place: flares, extinguishers, EPIRB or PLB, lifejacket gas cylinders, first-aid kit.
• Paperwork: yard or berth contract, your policy's lay-up conditions, renewals due next year.

Example lay-up record (fictional)

Fictional example: a 10 m (33 ft) sailing yacht with an inboard diesel and a saildrive, laid up ashore in a south-coast boatyard. The record fits on one page: what was done, at what engine hours, by whom, and above all what was disabled. That last list stops anyone starting the engine in April with its air intake still sealed.

• Header: lift-out on 6 Nov 2026, hour meter at 1,412 h, work done by the yard's engineer.
• Engine: oil and filter, two fuel filters, separator drained (a little water), tank brimmed with biocide, raw-water circuit flushed and antifreeze run through, saildrive oil changed, diaphragm sound, anode replaced.
• Water and heads: tanks emptied, calorifier bypassed and drained, antifreeze at every tap and through the heads.
• Hull: three small blisters below the waterline to starboard, photographed, to be looked at in spring.
• Power and safety: batteries taken home by the owner, liferaft away for servicing, flares to replace.
• To undo in spring: impeller removed (in the chart table), air intake and exhaust sealed, tag on the helm, seacocks left open ashore, calorifier on bypass, batteries, liferaft, sails.

Laying up several boats from one checklist

For a boatyard or management company, the hard part is applying the checklist identically on every boat, knowing who did what and finding the record in spring. In Captain Crews, marine management software, you save this checklist once as a work template called “Winterisation”, with a line for each boat and its technician. In one go, it creates one work order per line, and can do so again each year in the month you choose. The engine-hours step, once linked to the engine, updates its hours on the boat's record. Any step can take a comment (“impeller in the chart table”), and photos are time-stamped. In spring, the autumn job is in the boat's maintenance log.