When is it safe to de-winterize a boat, and what should I check first?
My boat has been ashore all winter with antifreeze in the engine's raw-water circuit and domestic plumbing. The days are warming up but we still get cold nights. When can I recommission it, and what should I check before launching and starting the engine?
Answer
De-winterise water-filled systems once the risk of freezing at your storage location has passed, or when you can reliably drain or protect them again before another frost. Check through-hulls, hoses and drain plugs first, then engine fluids and the cooling-water supply before launching or starting the engine.
Choose a frost-free window
A warm weekend is enough for cleaning, inspecting fittings and charging batteries. It does not mean it is safe to refill the plumbing. Check local overnight temperatures, the forecast for the next 7 to 10 days and your area's usual late-frost pattern. A forecast helps with planning but guarantees nothing.
Boats ashore can cool more quickly than boats afloat. Exposed pipes or cockpit showers may freeze while the cabin still feels comfortable. If frost remains possible, leave vulnerable systems winterised and finish the dry checks first.
Recommission systems separately. The engine may be ready for use while the freshwater tank, shower and toilet remain protected. Do not rely on an unattended cabin heater as your only frost protection.
Check hull openings and fittings
Before launch, check every underwater opening, including the engine intake, toilet intake and discharge, cockpit drains and any transducer fittings. A missing plug or split hose can turn launching into an emergency.
- Through-hulls and seacocks: inspect for cracks, corrosion and loose fittings. Operate each valve and check that its outside opening is clear.
- Hoses and clips: look for splits, hardening and corrosion beneath clips, especially where hoses join below-waterline fittings. Tighten securely without crushing the hose.
- Plugs and covers: refit any hull drain plug, engine drain plugs, raw-water strainer lid and fittings removed for winter, using the correct seals.
- Stern gear: inspect the propeller, shaft or saildrive, anodes and propeller locking arrangement. A conventional castellated nut needs its specified split pin; folding and feathering propellers have their own securing procedures.
Keep unnecessary seacocks closed for launch. Open and check each required circuit in turn. Once afloat, inspect every connection, the shaft seal and the bilge before leaving the berth.
Prepare the engine for starting
Read the winterisation record first to establish what was drained, disconnected or filled with antifreeze. Check engine and gearbox oil levels, belts, fuel hoses and filters. Reconnect anything deliberately removed during lay-up.
On a freshwater-cooled engine, check the expansion tank and the specified permanent coolant mixture. Permanent engine coolant normally stays in service; it differs from winterising antifreeze placed in the raw-water circuit. An engine cooled directly by seawater needs a different recommissioning procedure.