How often should I winterise my boat, and what maintenance should I include?
I have a 32-foot sailing yacht with an inboard diesel, sea toilet and pressurised freshwater system. I might leave her afloat this winter and use her occasionally. Should I winterise everything once a year, and what needs checking afterwards?
Answer
Winterise your boat once a year, before the first frost or at the start of a prolonged winter lay-up, and restore any frost protection disturbed by using the boat. Include engine servicing, cooling and water systems, batteries, hull fittings, rig and covers, then check the boat weekly throughout storage.
Plan for frost and storage
Start with the engine handbook, then identify everything that holds water: the engine cooling circuit, exhaust waterlock, freshwater pump, calorifier, toilet, shower and seacocks. Trapped water can cause expensive damage, even ashore.
If you sail through winter, service the engine and protect vulnerable systems between trips. Heating must keep the engine compartment and other vulnerable spaces above 0°C. A warm saloon does not guarantee a frost-free seacock. A frost guard needs reliable power and regular checks, so prepare for a shore-power failure.
If the boat stays afloat, check your insurance conditions for winter berthing, unattended periods and inspections. Plan a haul-out to inspect the hull and underwater fittings. An annual haul is a sensible starting point; adjust the interval to suit the boat, location and fouling.
Service engines and cooling circuits
Change the engine oil and oil filter before storage, following the handbook. Replace fuel filters when due, drain water from the separator and investigate contamination. Inspect belts, hoses, clips and the raw-water impeller, and check for leaks. Replace worn parts before recommissioning.
Cooling systems need different treatment:
- Freshwater-cooled inboards: check the sealed coolant circuit's antifreeze strength with a suitable tester. The separate seawater circuit still needs draining or antifreeze protection according to the engine manual.
- Direct seawater-cooled inboards: follow the specified draining and antifreeze procedure, including any thermostat-related instructions.
- Outboards and sterndrives: flush and drain as specified, store in the prescribed position and inspect gear oil for water contamination. Follow model-specific instructions for fogging petrol engines, particularly fuel-injected models.
Use the antifreeze type and concentration specified for each application. Colour alone does not identify compatibility. Collect discharged antifreeze for proper disposal. Never run an engine dry or feed water into a stationary engine unless its procedure explicitly requires it.
Inspect fuel hoses and tank fittings. Follow the engine maker's storage guidance for fuel level and stabiliser. Run engines only with adequate ventilation to prevent carbon-monoxide exposure.
Drain plumbing and maintain batteries
Empty freshwater tanks and drain the calorifier, pumps, strainers, taps and shower hoses. Switch off the calorifier's electric supply before draining it. Where draining leaves trapped water, use potable-water-system propylene-glycol antifreeze according to its instructions, bypassing the calorifier where appropriate.