How to Winterise a Boat in the UK: A Practical Winter Checklist

How to Winterise a Boat in the UK

The boat show season is behind us, the evenings are getting darker and, for a lot of UK boat owners, attention now turns to winter.

We may have had the hottest year on record and at the beginning of October, it is still shorts and t-shirt weather, but winter is just around the corner!

Some boats will be lifted ashore and left until spring. Others will stay in the water and keep being used through the colder months.

Either way, doing a bit of preparation now can save a lot of hassle — and potentially a lot of money — later.

Frozen pipes, flat batteries, damp interiors, storm damage and neglected engines are all far easier to prevent than fix.

So here’s a practical run-through of the things worth checking before winter really sets in.

Are you laying the boat up, or keeping it in use?

That decision changes what you need to do.

If the boat is coming ashore and won't be used for several months, you'll probably want to carry out a fairly thorough lay-up.

If it's staying afloat and you'll still be using it, you may not want to shut systems down completely. Instead, the focus shifts towards frost protection, battery condition, mooring security and regular checks.

Either way, don't just lock it up in October and expect everything to be perfect in April.

Start with the engine

This is one area where it pays to follow the manufacturer's guidance rather than relying on what someone else does with their boat.

Depending on the engine, winter preparation may include:

• changing engine oil and filters;

• flushing the cooling system;

• protecting it with the correct antifreeze;

• checking belts and hoses;

• inspecting the impeller;

• checking fuel filters; and

• lubricating moving parts.

Outboards may need flushing, gear oil checks, lubrication and fuel preparation too.

If you're not confident doing this yourself, get a marine engineer involved. A winter service is usually cheaper than repairing frost or corrosion damage later.

The Royal Yachting Association has useful guidance on engine winterisation and general seasonal maintenance.

Don't forget fuel and batteries

Fuel can cause problems when a boat sits unused for months.

On diesel boats in particular, condensation and contamination can become an issue. Check filters and follow the engine or fuel-system manufacturer's recommendations on storage and additives.

Batteries also need some attention.

A battery that is left discharged over winter may not have much life left by spring. If practical, lead-acid batteries can be removed and kept charged in a dry place. If they stay aboard, make sure they're being maintained correctly.

If your boat is remaining afloat, think before isolating everything. Bilge pumps, alarms or monitoring systems may still need power.

Drain or protect the water system

Freshwater systems are particularly vulnerable to freezing temperatures.

That can include:

• water tanks;

• pumps;

• taps;

• showers;

• toilets;

• calorifiers; and

• pipework.

If you're laying the boat up, drain the system thoroughly or use a suitable marine antifreeze where the manufacturer recommends it.

Don't assume that opening a couple of taps has emptied everything. Water often sits in low points, pumps and fittings.

And don't use automotive antifreeze in a drinking-water system unless it is specifically approved for that use.

Give the boat a proper clean

Not glamorous, but worth doing.

Salt, dirt, food and damp all contribute to corrosion, mould and unpleasant smells.

Wash the decks and superstructure with fresh water, empty the fridge, remove food, clean lockers and take bedding or towels home if possible.

If the boat is ashore, it's a good time to pressure-wash the hull and inspect areas you can't normally get to.

Inside, leave lockers and doors open where sensible so air can circulate. Future-you will appreciate it.

Check bilges, seacocks and pumps

A clean, dry bilge makes it much easier to spot a problem.

Check:

• bilge pumps;

• float switches;

• alarms;

• seacocks;

• skin fittings;

• hoses;

• hose clips;

• stern glands; and

• rudder glands.

If your boat is staying afloat, test the bilge pumps properly rather than assuming they're fine. Winter rain has a habit of finding its way into places you didn't know leaked.

Prepare for winter storms

In the UK, wind is often just as much of a concern as freezing weather.

If you're leaving the boat afloat, inspect mooring lines and consider extra protection against chafe. Check fenders and make sure they're positioned for the likely range of wind directions and water levels.

If the boat is ashore, make sure covers are well secured and won't turn into giant sails.

A badly fitted winter cover can cause almost as many problems as having no cover at all.

Sailing boat? Give the rig some attention

Winter is a good time to inspect sails, rigging and deck gear.

Look at:

• standing and running rigging;

• terminals;

• shackles;

• split pins;

• furling systems;

• spreaders; and

• mast fittings.

If sails are coming off, store them somewhere dry.

You don't necessarily need to unstep the mast, but it's worth considering exposure, rig condition and any requirements from your marina or yard.

Fight damp early

Boats are extremely good at becoming damp when nobody is using them. Ventilation helps.

Take soft furnishings home if you can, prop cushions up, open lockers and allow air to circulate.

A suitable dehumidifier can be useful where safe shore power is available and your marina allows it, but don't leave electrical equipment running unattended without thinking through the risks.

Check your insurance

Winter storage doesn't mean the boat is risk-free.

Fire, theft, storms and accidental damage can all happen ashore as well as afloat.

Check whether your policy has any requirements around:

• lay-up;

• storage location;

• moorings;

• cruising limits;

• security; or

• winter conditions.

If you've moved the boat somewhere different for winter, check whether your insurer needs to know.

Make a list of what you've done

This sounds basic, but it's one of the best tips.

Write down anything you've disconnected, drained, blocked off or removed.

If you've taken out an impeller, disconnected a pipe or isolated an intake, make it obvious.

Six months is plenty of time to forget.

Should you service the boat now or wait until spring?

For many jobs, autumn makes more sense.

Old oil contains contaminants. Small problems don't improve by being left for six months. And marine engineers are usually much easier to book in winter than during the first warm weekend of April.

Get the boring jobs done now and spring becomes about launching the boat, not fixing it.

A simple winterisation checklist

Before you leave the boat for any length of time, check:

• engine and cooling system;

• fuel and filters;

• batteries and charging;

• freshwater and plumbing;

• bilges and pumps;

• seacocks and hoses;

• hull and anodes;

• mooring lines and fenders;

• sails and covers;

• interior ventilation;

• shore power and electrics;

• insurance arrangements.

And keep a note of anything that needs reversing before the boat goes back into use.

Winter is also when boat owners start browsing

Once the maintenance is done, there's another winter tradition.

Looking at bigger boats.

If your thoughts are turning towards changing or upgrading, Boats On Finance lets you browse boats currently for sale and explore what different monthly budgets could potentially buy.

And if you want to understand how the finance might work, SALT specialises in leisure marine finance.

Our process is digital, but the team behind it understands boats, buying, surveys, dealers and the realities of ownership.

Sometimes you don't need another calculator. You just need to talk to someone who gets boats.

Frequently asked questions

When should I winterise my boat in the UK?

Ideally before the first proper cold weather arrives. Autumn is the sensible time, particularly if you need a lift-out, storage space or a marine engineer.

Do I need to winterise a boat that stays in the water?

Not necessarily in the same way as a laid-up boat, but you should still prepare it for colder weather. Pay particular attention to plumbing, engines, batteries, bilge pumps and mooring lines.

Can I leave my boat in the water all winter?

Yes, many UK owners do. The boat, berth and insurance arrangements need to be suitable, and the boat should be checked regularly.

Should I remove my boat batteries for winter?

It depends on the boat and battery type. Lead-acid batteries may benefit from being removed and maintained ashore, while boats left in the water may need batteries connected for pumps or monitoring systems.

Does a boat need insurance while stored ashore?

There is no general legal requirement for private leisure boat insurance in the UK, but marinas, lenders and other organisations may require it. Theft, fire and storm damage also remain risks while the boat is ashore.

Final thought

Winterising a boat isn't complicated, but neglect can become expensive.

A day spent cleaning, checking and protecting the boat in autumn can save days of repairs in spring.

Do the jobs now. Then spend winter planning where you're going next year.