Winterisation of Inboard Engines

When the nights are drawing in and the temperature is cooling off, it is time to start thinking about preparing your boat for storage during the winter months.

‘Winterising’ an engine is a key maintenance task for any boat owner.  Failure to do so could mean more work in the Spring and more expense.

Your local engineer will be able to advise you on the necessary tasks that need to be carried out to prepare your engine.  You should also find these listed in your Owner’s manual.  However, as a general rule, it is recommended that the following procedures should be carried out:-

  • Check the cooling fluid – Vital to protect the inside of your engine, it is recommended that the mixture is 50% water and 50% anti-freeze.  Ideally it should be replaced annually as overtime it loses it’s anti-corrosion properties.  Top it up to the maximum level in the heat exchanger.
  • Drain the engine oil and refill with new oil – Bring the engine up to temperature to ensure oil is hot.  Replace the oil filter.
  • Rinse seawater cooling circuit with freshwater  – Close the sea cock and disconnect the hose on the outlet side of the raw water pump.  Disconnect the cooling water discharge hose from the exhaust manifold or riser.  Run fresh water into the discharge hose to back-flush raw water passages and rinse out salt deposits.  You can extend the disconnected pump hose outside the boat or let the bilge pump handle the flush discharge.  Remove and rinse the impeller as anti-freeze can sometimes swell the rubber.  It is probably best to leave it out until spring, in a dry place, sheltered from light.
  • Close the engine air intake – To avoid moist air getting inside your engine, ensure you seal air inlets, crankcase and transmission breathers, exhaust outlets and tank vents by creating an airtight seal.  Making caps from plastic containers and then taping them into place is an ideal solution.
  • Drain the engine oil and refill with new oil  – Bring the engine up to temperature to ensure the oil is hot.  Replace the oil filter.
  • Release belts tension – Slacken the alternator adjuster to release the tension on the drive belt, helping to prolong the life of the belt.
  • Drain water lock – The less moisture the engine is exposed to, the less corrosion will occur.
  • Dry the boat’s bilge under the engine -This is a mucky job but well worth doing to avoid leaving a lot of moisture which is liable to corrode the engine.
  • Spray the engine with a water-repellent product This will help safeguard against corrosion.
  • Fill Fuel Tank This will help avoid condensation.  Tighten the deck filler as water can puddle when the boat is ashore.