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How To Winterise Your Outboard

How To Winterise Your Outboard

Preparing your outboard for winter is a crucial aspect in prolonging its life and preventing any damage, when neglected it can cause you a costly spring in parts and repairs. Here we will take you through the important steps that you can carry out at home to protect and maintain your 4-stroke outboard

It is worth mentioning that if you do not feel confident carrying out any of these jobs then seek professional guidance, you should also follow the guidelines for your specific outboard as methods may vary slightly.


     1) Change The Oils

It is important to change the oils before winter as the oil can lose its properties over time and become contaminated. So it is a good idea to get fresh oil in for the cold period.

For engine oil remove the oil sump drain plug, with a catch pan underneath of course (you may want to wear gloves for this). Once all the oil is out, reattach the oil sump drain plug to the manufacturers specification with a torque wrench, being careful not to cross-thread when tightening it. To refill the engine oil, take out the dipstick and fill up to the manufacturers guidelines, then check the dipstick after. For Orca engine oil see here.

For gear oil. It is always best to follow manufacturers instructions but generally you should remove the bottom drain screw on the lower leg until fully empty. Unscrew the top screw and then you should refill from the bottom, so as to create a vacuum of gear oil with no trapped air. Once oil starts to come out of the top hole, the gearbox is full. For Orca gear oil see here.

      2) Cooling Systems Flush

Next up it is necessary to flush through the cooling system to get rid of salt deposits that can cause corrosion. It is essential not to leave this festering over winter. Fresh water is usually used for this but we would highly advocate mixing the water with Blu Thru to ensure your outboard is flushed completely. Blu Thru is a safe and fast system for residue removal and reducing corrosion in the cooling chambers and heat risers of your outboard, leaving a waxy protective layer that will protect as well as lubricate. It works by mixing with water as it enters the inlets, flushing through as it goes. For Blu Thru kits see here.

Flushing your cooling system can vary from outboard to outboard. The main options are to either use flush muffs or a freshwater tank such as a big bucket. Other engines such as the Orca 15, 20 and 25hp now have a specific hose flush point for this job, so it is worth checking this first. If you are using flush muffs you should attach them to the water intakes on the outboard, creating a good seal, and then have the hose flow water through continuously. If you are using Blu Thru which we highly recommend, attach the dispenser to the hose and place the tablets inside and flush through until the blue water turns clear. Allow time for any water still inside to fully drain afterwards.

      3) Fuel System

Leaving your fuel in the fuel tank for extended periods of time runs the risk of damage to your fuel system and tank. The fuel can form gums as it becomes stagnant and can clog lines, jets or injectors. Condensation can also form in the tank, especially with the E10 fuel as this has a short life span and can cause a lot of issues. As such we recommend leaving your fuel tank and system empty over the winter period.

To do this we advise managing your fuel consumption towards the end of the season so you can easily run your outboard dry of fuel as part of the winterising process. To run your outboard dry you can either disconnect the fuel line or turn off the fuel tap while the engine is running. This also forms part of the next step as you will need to run oil through the engine at the same time as the last of the fuel runs through and it cuts out.


      4) Engine Protection

There are two popular ways of protecting the internals of an outboard engine; After flushing your cooling system, keep the engine running and either run fogging oil or 2-stroke oil through it. You should disconnect or turn off the fuel supply mid doing this to run the engine dry of fuel simultaneously.

Firstly engine fogging. Fogging oil is an anticorrosive that will protect internal elements such as the cylinders, inside the carb, valves and pistons by preventing any rust. This oil is applied by running it through the engine to coat parts with a protective layer, for this you will need to take out the fuel drain plug on the carburettor. Then with the engine running at a mid-idle, spray the fogging oil into the carb, the engine will smoke as it makes its way through. As the engine runs out of fuel and begins to run rough, carry on spraying the oil through the carb inlet up until the engine runs out of fuel and cuts out.

Another method is to use 2-stroke oil for a similar process. This is useful for coating all around the cylinders as well as the valves. First take the fuel drain plug out of the carburettor and squirt the oil straight in there, once the oil starts to get through and the engine begins to smoke; Squirt the oil a few times into the air inlet just before the carburettor. Like with the fogging oil try to time this with the engine running out of fuel.

       5) Grease

Once at this stage it is a good idea to undertake some general maintenance of the outboard.

This should include greasing any moving parts such as cables. In particular you should look to grease the transom tilt pin, hold tilt mechanism, transom tube and the swivel bearing transom clamps. Also, taking the prop off and greasing the shaft before placing it back on is a good idea.

Note: you may need a grease gun to reach some areas.


      6) Wash & Clean

Washing and cleaning your outboard is an essential but often overlooked aspect of winterising.

Firstly it is a good idea to give your outboard a good wash all over, before waxing it, to protect the paintwork.

You can also take this time to touch up any scratches or chips to prevent oxidising and rust forming.



      7) Storage

The last thing to consider when winterising your outboard is how you store it. Most of the time leaving your outboard stored vertically is optimal, this is usually done with an engine stand. However, if this is not convenient then either tiller arm down or tiller arm up, whatever is recommended for your outboard by the manufacturer.

For bigger outboards with electric starts, you should store the battery away from the cold for the winter and charge every month or so, as they tend to deteriorate quickly in steady cold temperatures.



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Comments (2)

  • Rob Shepherd Reply

    What about doing a 2 stroke winterising article. There are many 2 strokes out there still!

    26 October 2021 at 6:35 am
    • Nicola Middleton-Groom Reply

      Hi Rob, thanks for your message. We can look at doing one of those moving forward but as a company, we don’t stock 2 stroke engines so we thought it best to create the content which would relate to our product mix. I’ll add this to the marketing list and we’ll get round to it soon.:-)

      2 November 2021 at 10:14 am

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