Lay-Up Season, Sorted: A Thrifty Winterising Plan for UK Boats in 2026

By early November 2026, the UK boating calendar has already flipped from lazy summer evenings to frost-on-the-coachroof mornings. Whether your boat lives on a swinging mooring in the Solent, a muddy pontoon on the Norfolk Broads, or a canal arm near Braunston, the winter lay-up is less about making everything shiny and more about stopping small jobs becoming spring bills. The aim is simple: a boat that wakes up without a cracked block, a damp cabin, or a battery flatter than a pub garden in February.

Here's the no-nonsense routine I'd use on my own boat this month. It leans hard on DIY, avoids chandlery potions that cost more than they save, and works for both salt-water sailors and inland cruisers.

Start With a Walk-Through, Not a Shopping Spree

Before you buy a single litre of antifreeze, spend an hour on board with a notebook and a phone camera. Photograph the engine bay, battery connections, seacocks, water pump, calorifier and any awkward hose runs. Note what's already tired. That dodgy impeller cover or weeping hose will be much easier to sort now than in an icy March. A quick walk-through also stops the classic mistake of buying a trolley-load of winterising gear while missing the one split hose that actually matters.

Work from bow to stern and make a short list: jobs you can do, jobs a mate can help with, and jobs that genuinely need a professional. A rigging check or gas safety inspection is not the place to channel your inner YouTube mechanic.

Engine: Flush, Fog and Don't Ignore the Impeller

For raw-water-cooled engines, flushing with fresh water is the first win. Run the engine on muffs or in a bucket, then drain the raw-water side properly. If you're using antifreeze, use propylene glycol marine antifreeze mixed to the strength on the bottle, not neat pink stuff poured in hopefully. A cheap refractometer antifreeze tester from a motor factor is worth its weight in gold and costs far less than a cracked heat exchanger.

Fogging oil is old-school but still sensible for petrol inboards and outboards. Follow the maker's method, not a forum argument. While you're in there, check the impeller. If it's been in service for a couple of seasons, replace it now. A water pump kit is cheap compared with an overheated engine.

Fuel matters too. Top up diesel tanks to reduce condensation, add a reputable fuel stabiliser, and change fuel filters before lay-up rather than after. On canal boats, check the weed hatch, stern gland and engine mounts while access is easy. Common mistake: running the engine after draining the raw-water side without a water supply. That's a fast route to a toasted impeller.

Freshwater Systems: Drain, Bypass and Think About Spring

Empty the freshwater tank, open the taps, and run the pump briefly to clear the lines. Don't forget the shower head, transom shower and any deck wash. If you have a calorifier, follow the manufacturer's winterising advice; some need bypassing or draining separately. Pour food-grade antifreeze into sink and shower traps, but never into the drinking-water tank unless the product is explicitly rated for potable systems.

On a narrowboat, the water pump and accumulator often sit in a cold engine room. A £10 aquarium siphon or a simple hand pump can save a lot of swearing. Another common miss: leaving water in the pump body or filter housing. Drain it, dry it, and leave a note for spring.

Batteries: The Cheapest Winter Crew Is a Smart Charger

Batteries hate being left partially charged in the cold. Remove portable batteries if that's practical, and store them somewhere cool but frost-free. For batteries staying on board, clean terminals, check electrolyte levels if serviceable, and connect a smart charger with a maintenance mode. A mid-priced CTEK or Victron unit will do more for battery life than any miracle additive.

Solar can help, but only if the panel stays clear and the controller is decent. A cheap controller can drain a battery in low light. If you're on shore power, don't leave a dumb charger cooking the battery for five months. Check the charger's float voltage and use a timer if needed. Common mistake: isolating the battery but forgetting the bilge pump or alarm. Decide what must stay live and label it.

Canvas, Covers and the Mould Wars

Clean canvas while it's still mild enough to dry. Dirt traps moisture, and trapped moisture means green stains by spring. Use a gentle canvas cleaner or a very mild soap solution, rinse well, and reproof with a product such as Fabsil Gold once fully dry. Don't armour the boat in a giant tarpaulin that can't breathe. Airflow beats airtight every time.

For below decks, a crystal dehumidifier or a couple of old socks filled with cat litter will soak up winter damp. Leave lockers open, lift cushions, and remove bedding. White vinegar diluted in water is a good first line against mildew on hard surfaces. Common mistake: sealing the boat up like a Tupperware box, then wondering why the cabin smells like a wet dog by February.

Through-Hulls, Seacocks and the Inland Difference

Coastal sailors should exercise seacocks, check hoses and clips, and leave them in the position recommended by the maker. Don't force a stiff seacock; deal with it now. Canal boaters have different priorities: drain and protect the domestic water system, check the stern gland, clear gutters and make sure the bilge is dry. A damp bilge plus frost is a recipe for cracked pipework.

The Small Chandlery Kit That Earns Its Keep

You don't need a pallet of products. A sensible lay-up kit looks like this: a refractometer antifreeze tester, a decent funnel, spare hose clips, silicone spray, cable ties, oil absorbent pads, a smart charger, a couple of crystal dehumidifiers, and a roll of labelling tape. Buy consumables like antifreeze, oil and cleaning cloths from motor factors or bulk suppliers where the price per litre makes sense. Save the chandlery trip for marine-specific parts that actually need to be marine-specific.

Final Lock-Up Check

Before you leave, take photos of everything you've disconnected, label isolators, empty the bins, and leave a note in the cabin listing jobs for spring. Close seacocks as advised, check mooring lines for chafe, and make sure the cover is secure but ventilated. Winterising isn't glamorous. But a quiet, dry boat in March is its own kind of reward.