There is a particular afternoon in late October when the light goes flat, the wind carries a bite, and every sailor on the pontoon seems to be coiling ropes with a resigned sort of haste. Winterising is not the most glamorous job in boating, but it is the one that quietly pays you back in spring. A boat laid up with care will reward you with a dry interior, a willing engine and topsides that still gleam when the cover comes off. A boat left to fend for itself through a British winter will hand you a bill.

What follows is the sequence we would follow ourselves, working from the inside out and finishing with the outside in. Set aside two full days if you can, and take your time. Rushing the job is how things get missed.

Start With the Water Systems

Fresh water left in pipes and tanks is the single most common cause of spring misery. It freezes, expands and splits fittings you will not find until you next turn on a tap. Begin by emptying the fresh water tank completely — pump it through rather than just opening the drain, so the lines are as clear as you can get them.

• Run the taps until the tank is dry, then flush the system with a food-safe antifreeze if your boat is likely to see hard frost. The pink propylene glycol type is the usual choice; never use automotive antifreeze in a potable system.
• Pour a little antifreeze down each sink, shower drain and bilge outlet so the traps and through-hulls are protected.
• Empty and dry the calorifier or water heater, and leave its drain plug out.
• Remove the heads inlet and outlet hoses if you can, or at least pump them dry and dose them with antifreeze. Seacocks should be closed and, ideally, exercised before you leave them for the season.

Leave every locker and cabin door open a crack so air can move through. Damp, still air is what grows mildew on cushions and varnish.

Service the Engine Before You Lay It Up

An engine that goes into winter with dirty oil inside it will corrode from the inside out. Change the oil and filter now rather than in spring — the contaminants you remove are the ones that would otherwise sit against bearing surfaces for five months.

• Fill the fuel tank to the brim to minimise condensation, and add a diesel biocide and stabiliser.
• Change the fuel filters and drain any water from the sediment bowl.
• Flush the raw water circuit with fresh water, then draw antifreeze through the seawater pump until it exits the exhaust. This protects the heat exchanger and the raw water pump impeller.
• Fog the cylinders: remove the injectors or spark plugs, squirt a little preserving oil into each bore and turn the engine over by hand a couple of revolutions.
• Loosen the alternator belt and smear a little grease on exposed metal and electrical terminals.

If the boat is coming ashore, this is also the moment to check the anodes, the stern gland and the propeller for play. A job half done on the hard in November is far easier than one done on a swinging mooring in January.

Protect the Topsides, Deck and Rig

The outside of the boat takes the worst of the weather, so give it a proper defence. Wash the hull and topsides thoroughly to remove salt and grime, then apply a good coat of wax — a waxed gelcoat sheds water and dirt, and it makes spring cleaning a morning's work rather than a week's.

• Remove and stow sails, sprayhood, dodgers and any canvas that can be taken home. Damp canvas left on the boat will mildew.
• Cover the boom and, if the mast stays up, tape over the sheave boxes and check the rigging for cracked terminals or rust weep.
• Check stanchion bases, cleats and winches for movement, and grease winches before the cold sets in.
• Clear the scuppers and cockpit drains; a blocked drain can fill a cockpit and find its way below.
• If you are leaving the mast up, slacken the rigging very slightly and check the masthead wind instruments.

A decent cover, well tensioned and with ventilation gaps, is worth more than three cheap ones that flap themselves to shreds by Christmas.

Look to the Batteries and Electrics

Batteries dislike cold and they dislike being left flat even more. Take them home if you can, store them somewhere frost-free and give them a top-up charge every month or so. If they stay aboard, isolate them, and consider a small solar maintainer to keep them topped up.

• Clean terminals, apply petroleum jelly and check every fuse and connection you can reach.
• Remove any electronics that are easy to unplug — handheld VHF, plotter cards, binoculars — and store them dry.
• Leave a couple of moisture absorbers in the cabin, and check them monthly.

Make a Spring Checklist as You Go

Finally, keep a notebook with the boat. Every time you spot something that needs doing, write it down — a seized seacock, a tired impeller, a small leak at the hatch. Come March, that list becomes your launch plan, and you will not spend the first fine weekend of the year trying to remember what you noticed in November.

Winterising is really an act of optimism. You are betting on the spring, and doing the work now so that the first sail of the season is a pleasure rather than a repair bill. Look after her through the cold months, and she will be ready when the light comes back.