Boat winterization checklist — engine, water systems, hull and interior

Winterization is the one service where a missed step costs more than the whole job: a cracked block, a split water heater, a mildewed interior. This checklist is in the order the work should happen, from the last run of the engine to the last look before you leave. It suits a 30–100 ft boat laid up afloat or ashore in a climate that freezes; in warm-water fleets, use it as a lay-up list without the antifreeze steps.

Before you start

• Fill the fuel tanks to 90–95% and add a stabiliser; run the engine long enough to get treated fuel to the injectors. Full tanks mean less condensation and less water in the fuel in spring.
• Pump out the holding tanks and flush them; a tank left full over winter is the worst job you will face in April.
• Photograph every system before you touch it — where the hoses run, which sea cock feeds what. The photos are the commissioning guide.

Engine and generator

• Change the oil and filter while the engine is warm; used oil is acidic and eats bearings over a winter.
• Change primary and secondary fuel filters; check the primary bowl for water.
• Close the raw-water sea cock, disconnect the intake hose and run the engine on a bucket of non-toxic (propylene glycol) antifreeze until it comes out of the exhaust pink. Same for the generator.
• Remove the impeller, inspect and store it loose (or replace in spring) so the vanes do not take a set.
• Check the closed-circuit coolant strength with a refractometer; top up or replace to the manufacturer's freeze rating.
• Drain the exhaust water lock (muffler) if it has a drain; otherwise the antifreeze run covers it.
• Slack the belts, spray the engine with a light corrosion inhibitor, seal the air intake and exhaust outlet against damp and animals.
• Outboard: run dry of fuel or fog the cylinders, flush, drain the gear oil and check for water, store upright.

Water systems

• Fresh water: drain the tanks, pump the system dry, bypass the water heater (do not fill a heater with antifreeze), then pump non-toxic antifreeze through every tap, shower, and deck wash until each runs pink. Drain the heater completely.
• Watermaker: pickle per the manufacturer's manual — the membranes must not freeze and must not dry out.
• Bilge: pump dry, clean, leave the float switches working and the batteries able to run them if the boat stays afloat.
• Air conditioning and fridge raw-water loops: flush with antifreeze; drain the strainers.
• Deck shower, washdown pump, ice maker, dishwasher, washing machine: every one has a pump and a trap that will freeze.

Hull, deck and rig

• Ashore: block and chock properly, sea cocks open (so no water sits in them), bungs out, cockpit drains clear. Afloat: sea cocks closed except cockpit drains, double lines, chafe gear, fenders checked monthly.
• Anodes noted for replacement in spring; hull washed off before the growth hardens.
• Sails off, washed, dried and folded; running rigging removed or at least halyards replaced with messenger lines to spare the sheaves and the UV.
• Canvas, biminis and cushions ashore and dry; covers on with plenty of ventilation.
• Winches and windlass: wash, dry, light oil; a winter is when salt does its worst.
• Battery: charge fully, then either keep on a smart charger or disconnect and store warm; check monthly. A flat battery freezes at a much higher temperature than a charged one.

Interior

• Everything soft that can come off the boat comes off; what stays is stood up on edge so air moves round it.
• Lockers, bilge access and floorboards open; fridge door propped open and dry.
• Two or three moisture absorbers or a low-wattage dehumidifier on a drip loop if there is shore power; check monthly.
• Fire extinguishers and flares noted for expiry; gas bottles off and ashore.
• Electronics: remove what can be removed, clean and store dry; the rest under covers.

What to record

Write down what was done, what was found and what needs doing before launch — the cracked hose, the weeping sea cock, the anode that is due. A lay-up with no notes turns into a commissioning week of rediscovery.

Do all of this in iVessel — and more

iVessel turns this page into a checklist your crew or yard actually runs, and keeps the record for spring.

• Build your own winterization and commissioning checklists — the items you want, in the order you want — stored on the boat's account so they are there every year and cannot be lost with a crew change.
• Assign the checklist to a crew member or the yard; each item is signed off with a name and a time, so you know exactly what was done and by whom.
• Log every service — oil, filters, impeller, antifreeze — with the hours, and the parts come off the spares inventory automatically; the spring reorder list writes itself.
• Note issues found during lay-up as issues on the boat, with photos, so they are on the list before launch.
• Works offline in the yard and syncs when you are back in range. iOS, Android and web.

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