Seasonal · Checklist

Winterising your boat: the lay-up checklist

The jobs to do before winter, afloat or ashore, that stop frost, damp and stale fuel turning into a spring repair bill. With tick-off checklists.

Updated October 2026 · Independent guide

Short answer: service the engine before lay-up, flush the raw water side with antifreeze, fill the fuel tank, drain the water system, keep batteries charged, and keep air moving through the boat. Then reverse it all in spring.

On this page

Engine
Boat and systems
Afloat or ashore?
Recommissioning

Use the checklists below on the day. Ticks aren't saved, so print the page if you want a paper copy.

Engine

Service the engine and gearbox before lay-up: fresh oil, filters and impeller
Run the engine briefly after the oil change so new oil coats the internals
Flush the raw water side with fresh water and antifreeze (hose into a bucket and run until it empties). Draining alone can leave water to freeze
Check the coolant level and antifreeze strength on freshwater-cooled engines
Fill the fuel tank to reduce condensation over winter
Seal the air intake and exhaust (rags or bags) against damp and nesting creatures. If afloat, make sure the exhaust can't flood
Leave a note on the engine listing what you've blocked, for the spring

Boat and systems

Drain fresh water tanks, pipes, pumps and the water heater, or protect them with antifreeze suitable for drinking-water systems
Flush and drain the heads and holding tank
Charge the batteries fully. Keep them on a maintenance charger, or remove them if there's no shore power
Remove sails, cushions and electronics you can take home to dry and store
Open lockers and engine access panels to let air move
Arrange ventilation or low heat: a small tubular heater or a dehumidifier if you have shore power
Check covers, fenders and mooring lines if you're staying afloat

Staying afloat or coming ashore?

Coming ashore lets the hull dry out, makes antifouling easy in spring, and keeps the boat out of winter storms, but you pay for the lift and storage. Staying afloat avoids those costs, but someone needs to check the lines, bilges and batteries through the winter. Either way, check your insurance policy for lay-up conditions.

Recommissioning in spring

Work back through your lay-up list and unblock every intake and exhaust
Check oil, coolant and battery levels (a healthy resting battery reads around 12.5V)
Take a fuel sample from the bottom of the tank to check for water
Test-run the engine and check cooling water flows from the exhaust
A couple of weeks after launch, have the engine alignment checked once the hull has settled

Common questions

When should I winterise my boat?

Before the first frosts. In the UK that usually means October or November. Engineers are busy at lay-up time too, so book early if you want a professional to do it.

Do I need to winterise if my boat stays in the water?

Yes. Seawater left in the engine's cooling system can freeze, and damp and stale fuel cause problems afloat as well as ashore. You also need someone to check the boat through the winter.

Should I fill my fuel tank for winter?

Yes. A full tank leaves less room for air, which reduces condensation and water in the diesel.

How much does a professional winterisation cost?

It varies by engine and engineer. One published UK price list charges £65 for engines under 20hp and £95 over 20hp, plus parts.