Winter Boat Maintenance: The Complete Winterisation Guide

Winter can be challenging for boats and their owners alike. Whether you're a continuous cruiser braving the elements or laying up your boat for the season, proper winter preparation protects your investment and ensures you're ready to cruise when spring arrives. This comprehensive guide covers everything you need to know.

Planning Your Winter Strategy

To Cruise or Not to Cruise?

First, decide how you'll spend winter:

• Keep systems running
• Regular movement prevents freeze-ups
• Requires daily attention
• Can be rewarding but demanding

• More stable environment
• Easier to manage heating
• Less wear on engine
• Good for major maintenance projects

• Boat stored out of water or secured
• Systems drained and protected
• Minimal ongoing attention required
• Thorough winterisation essential

Engine Winterisation

For Boats in Use

If you're continuing to use your boat:

1. Check antifreeze concentration in the cooling system
2. Service the fuel system – Winter diesel treatment prevents waxing
3. Battery maintenance – Cold weather demands more from batteries
4. Oil change – Fresh oil protects through winter
5. Fuel tank – Keep topped up to reduce condensation

For Lay-Up

Complete winterisation includes:

• Drain and refill with fresh antifreeze mixture
• Check all hoses and connections
• Consider running engine briefly monthly

• Fill tank completely
• Add fuel stabiliser
• Change fuel filter
• Run engine to circulate treated fuel

• Change engine oil and filter
• Old oil contains acids that damage bearings
• Top up gearbox oil
• Check stern gland/shaft seal

• Close seacocks
• Drain strainers
• Consider antifreeze in the raw water side

Protecting Water Systems

Freshwater Plumbing

Freezing water causes split pipes and damaged fittings:

• Keep minimal heating to prevent freezing
• Insulate vulnerable pipes
• Consider trace heating for exposed runs
• Keep water moving in extreme cold

• Drain the entire system completely
• Open all taps and drain cocks
• Empty the calorifier
• Pump non-toxic antifreeze through the system

Pump and Filter Care

• Remove and store water pump if possible
• Drain all filters
• Leave valves open after draining

Hot Water System

• Drain the calorifier completely
• Open pressure relief valve
• Disconnect immersion if fitted

Heating Considerations

Solid Fuel Stoves

If you're staying aboard:

• Service chimney before heavy use
• Check fire rope seals
• Stock up on fuel
• Ensure adequate ventilation

• Carbon monoxide alarm functioning
• Fire extinguishers in date
• Flue stability checked
• Hearth in good condition

Diesel Heaters

• Service before winter
• Clean fuel filters
• Check exhaust system
• Test thermostat function

LPG Heating

• Have system checked professionally
• Ensure adequate cylinder storage
• Remember gas consumption increases dramatically
• Check flue terminals are clear

Electrical System Care

Batteries

Cold weather is hard on batteries:

• Keep batteries fully charged
• Check electrolyte levels (flooded batteries)
• Clean terminals and apply petroleum jelly
• Test battery condition

• Fully charge before storage
• Consider removing and storing warm
• If left aboard, use a maintenance charger
• Disconnect if not charging

Shore Power

• Check cable connections regularly
• Ensure proper drainage away from sockets
• RCD test monthly
• Consider surge protection

12V Systems

• Turn off non-essential circuits
• Check for parasitic drains
• Service bilge pump (essential to keep running)
• Check navigation lights still work

Hull and Exterior

Steel Hulls

Winter is often when boats come out for:

• Hull inspection
• Blacking or painting
• Anode replacement
• Weld repairs

GRP Hulls

• Check for osmosis signs
• Inspect for impact damage
• Antifoul preparation

Deck and Exterior

• Clear gutters and drainage
• Check window seals
• Service hatch mechanisms
• Cover vulnerable fittings

Covers and Tarpaulins

If covering your boat:

• Ensure adequate ventilation underneath
• Create a frame to prevent pooling
• Check regularly for damage
• Secure against winter storms

Interior Winterisation

Ventilation

Crucial for preventing damp:

• Never completely seal the boat
• Use desiccants or dehumidifiers
• Open lockers and cupboards
• Remove soft furnishings if laying up

Soft Furnishings

• Store cushions upright or remove
• Use fabric fresheners
• Check for mould regularly
• Consider storage bags

Food and Provisions

• Remove all perishables
• Empty fridges completely
• Leave fridge door propped open
• Check for pest entry points

Security

Physical Security

• Check all locks work
• Consider additional padlocks
• Secure hatches and portholes
• Remove valuables

Insurance Considerations

• Notify insurers of lay-up period
• Check policy requirements
• Consider immobilisation requirements
• Keep documentation updated

Monthly Checks (If Laid Up)

Even laid-up boats need attention:

1. Visual inspection – Look for problems
2. Ventilation – Ensure air is circulating
3. Bilges – Check for water ingress
4. Mooring lines – Adjust for water levels
5. Batteries – Check charge state
6. Run engine – If safe and practical

Spring Recommissioning

Start preparing for spring:

• February: Order any parts needed
• March: Begin recommissioning checks
• April: First test cruise
• BSS: Book examination if due

BSS Considerations

Winter is an excellent time to:

• Address any BSS issues identified
• Prepare for upcoming examinations
• Schedule pre-season inspections
• Complete gas system servicing

Final Thoughts

Proper winterisation is an investment in your boat's longevity and your spring cruising enjoyment. Take the time to prepare properly, and you'll avoid costly repairs and frustrating delays when the weather improves.

If you're unsure about any aspect of winter preparation, or if you'd like a pre-winter safety check, don't hesitate to get in touch. A small investment in professional advice now can prevent expensive problems later.