How to Winterise Your Boat

Photo: Winter in Braunston (photo by Carmen Smith)
Created on 23/09/2014

Updated: 5th October 2018

As the days get cooler and the leaves on the trees start to change colour and fall to the ground, it’s time for boaters to start thinking about getting their boat ready for winter. This is particularly important if you plan to leave it moored up for the duration, but even if you’re planning on using your boat through the winter months, it’s worth giving your boat an annual once-over.  

Maintaining your boat externally and internally will keep your boat looking at its best, extend the life of its engine and other parts, and minimise any damage that could occur over the winter.

1. Have a checklist

It is a good idea to create a checklist before you start to ensure nothing is missed. With different boat sizes and types, come different systems to check. If your boat has a service manual, reading through it will help with tasks such as replacing fluids and parts properly. Information on winterising your boat should be provided in the section either called ‘lay up’, ‘cold weather’ or ‘extended storage’. 

Things to add to your checklist might include:

  • Gather all tools and new parts, fluids to use to winterise your boat.
  • Take out kitchenware, linen, blankets to wash and remove any food (if not using your boat over the winter)
  • Clean the inside of your boat
  • Change the engine oil and replace oil filters
  • If possible leave diesel tanks full as this reduces the amount of condensation (and ultimately water that will end up at the bottom of the tank).
  • Drain raw water cooled engines completely (not forgetting to close intake afterwards)
  • With fresh water cooled engines with a closed cooling system, drain the coolant and fill with half water and half antifreeze
  • Disconnect and clean the batteries
  • Take out the batteries of your smoke alarm and carbon monoxide alarm (if not using your boat over the winter)
  • Flush the water and holding tank
  • Flush the freshwater tank
  • Drain and leave the freshwater tank empty (if not using your boat over the winter)
  • Drain and put antifreeze in all radiators and pumps.
  • Allow air to circulate inside the boat.

2. Tool/Parts Preparation

Gather together all the new parts that may need replacing for example impellers, oil filters, and air filters etc.  Make sure you have all the fluids that need replacing such as oil, anti-freeze and corrosion inhibitor.

3. Cleaning Inside the Boat

If you are not using your boat over the winter season, take out any kitchenware to wash, empty the icebox and wash linens or blankets so that when you return to your boat in the spring there won’t be any nasty smells or moulds. Remember to remove any food or anything else that may attract rodents. When everything has been cleared, clean the inside of the boat from the floor to the cupboards and even down in the bilge.

4. Cleaning Outside the Boat

Give your boat a good clean on the outside; getting rid of any vegetation and mould.  Afterwards inspect your boat’s exterior checking for any damage or leaks. If anything is found get this checked by an expert.

Photo: A bit of spit and polish at Braunston (photo by Angela Acott)

5. Winterising Your Engine

This task will take the longest and will be messy. If you have been using your boat during the summer it is likely there will be a build up of by-products, water and acid which can lead to corrosion. Changing the oil is therefore important to decrease the chance of loss of power, poor fuel economy or engine failure.

Change your engine oil and replace the filters. It is also a good time to drain raw water cooled engines completely (not forgetting to close intake afterwards) and with fresh water cooled engines with a closed cooling system, drain the coolant and fill with half water and half antifreeze.

It’s a good idea to get your diesel tank filled up before leaving your boat for the winter, as this will reduce the amount of condensation that occurs in the tank.  Any condensation will end up in the bottom of the tank as water, which can provide the right conditions for diesel bug (contamination of diesel by bacteria) or ultimately the water getting into the engine.

Thoroughly grease the steering and control parts, working into the joints and check it all moves easily.

Photo: Keel cooled Beta Marine engine

6. Batteries

Disconnect the batteries and give them a clean because they can be expensive to replace. Some boat owners take the batteries away with them to charge over the winter while others choose to leave them in the boat fully charged. Some boats may need the batteries kept in for the bilge pump to continue operating.

7. Smoke and Carbon Monoxide alarms

Take out the batteries of your smoke alarm and carbon monoxide alarm if you are leaving your boat over the winter and store them in a warm and dry place; this will maintain their useful battery life.

8. Plumbing

Flush out the toilet with water and then pump out the holding tank.

Before flushing your fresh water tank, pull the circuit breaker or remove the freshwater pump fuse. Some freshwater tanks come with a drain on the bottom or a filter close to the water pump allowing the tank to drain out water.  You may want to add some non-toxic antifreeze directly through the water tank and plumbing. If you are leaving your boat for the winter leave the fresh water systems drained down and empty.

Photo: Toilet pouring at IWA National Festival at St Ives

9. Antifreeze

Drain and put antifreeze in all radiators and pumps.

10. Leaving the Boat

It’s worth checking whether there are any liquids in containers around that may burst when frozen. Remember to open any internal doors to allow air to circulate inside you may also want to add any moisture and odour absorbers just before you close up the boat.

Photo taken by Laurence White

11. Check your boat regularly

If you are away from your boat during the winter don’t forget to regularly check everything is ok with your boat as this will minimise the chances of any serious damage occurring over the winter, should something go wrong. Things to check include:

  • Making sure the engine is working and if needed, charge the batteries
  • Make sure the covers haven’t moved and that the boat is watertight
  • Ensure the mooring ropes are secure and loose enough for fluctuation in water levels when the boat is left unattended
  • Remove any build up of rainwater and leaves, clear the cockpit drains
  • Check the bilge pump is working.

Photo: Winter above Grindley Brook, Llangollen Canal (photo by Alan Wilding)

Top Tip

It may help the first time winterising your boat making a note of what tools you have used during the process, you can then keep all the tools used together for the next time you winterise your boat.

Going Boating This Winter?

If you are planning on going boating this winter, you can take a look at our winter boating guide.

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Tags: How-to Guides, Boating