How To Winterize An Outboard Motor? (Keep Your Boat In Shape For Summer)

If you’re planning on keeping your boat docked for a month or more, then you should winterize your outboard motor even if it isn’t winter yet.

Winterizing, as you might expect, normally means getting your motor prepared for the cold months, where you aren’t using your boat.

But if the summer season is unusually rocky and unsafe, then you will need to use the same technique!

Making sure that the motor is well treated whilst it is on vacation. 

If you decide not to winterize your outboard motor, then you can seriously damage the machine.

Poor maintenance is more likely to break your motor than high usage, and leaving your equipment salty and wet can erode important parts of the motor.

Your motor should be correctly stored and cleaned before any long period of non-use. 

If you’re not sure how to winterize the outboard motor, then here are some easy steps to help you through the process.

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Step 1 - Stabilize the fuel

Fuel Stabilizer is an important tool that stops fuel from oxidizing.

If fuel oxidizes it goes stale, meaning it will lose a significant portion of its power.

Treating the fuel like this will keep it healthy and in good condition for the motor. 

Really the fuel should be stabilized with every top up, but if time has run away with you then be sure to treat it during the winterization period.

How To Winterize An Outboard Motor

Step 2 - Protecting the inside

Most outboard motor handbooks suggest using a fogging spray to protect your motor, but 4 stroke engines would be better with a protective film.

To do this you will need to add 2 stroke oil to your fuel tank.

The ratio of which should be 1 part oil to 100 parts petrol, leaving a film of oil to protect the valves and cylinders.

For 4 stroke engines, this is important as fogging sprays may not reach the values. 

For 2 stroke engines fogging spray is just the stuff you need.

All you have to do is spray the fogging oil straight into the throat of the carburetor.

Make sure that the throttle is increased when you do this, otherwise, the engine might start to stall.

Better yet, try to run the carburetor out of fuel when you have finished with the fogging process. 

Step 3 - Clean the engine

To clean the engine you simply need to flush out all of the saltwater which would otherwise cause corrosion.

Use clean water to make sure your engine is glistening.

Really, this flushing technique should be done after every trip, but again if you are only going to do it once a year then do it in the winterization process. 

Now the engine has been flushed, make sure it is fully drained of any remaining water.

Trapped water can break an engine due to freezing, so take this part very seriously.

Step 4 - Keeping it greased

The best type of grease for your motor would be a water resistant grease gun.

Having a grease gun will allow you to get to the hard to reach places.

Typically those hard to reach places, are also the ones most in need of a good greasing.

Make sure to cover the propeller shaft and all the moving parts.

They need to be well coated for easy movement.

Whilst you are maintaining the moving parts, it’s good to make sure the outside of the motor is looking sharp too.

Use boat shampoo to give it a shine, finishing up with a good wax and polish.

Step 5 - Check and Change

Now you need to check the spark plugs, and change the fuel filters and lower unit gear oils. 

If you own a 2 stroke engine, then you will need to take special care with the spark plugs.

A lot of problems associated with 2 stroke engines come from poor quality spark plugs.

When you check them, you are looking for any irregularities with the electrodes and the electrode’s gap.

It’s better to be safe than sorry, so if you see an issue get yourself a new spark plug.

Changing the fuel’s filter is best done at this stage when your engine is clean. 

To change the lower unit gear oil, you should check with the motor’s manual as each one will require different levels of quantity.

Once you’ve done that, you should be able to find the gearbox right in front of the propeller.

It should have a stainless steel screw-like draining plug and a vent just above it.

Follow the manual to best help you change the gear oil correctly.

Step 6 - Storing the engine and battery

Now that the motor is cleaned and ready for a rest, you need to know how to keep it safe in storage.

The best place to keep an unused engine is out of water.

This way you can have it stored vertically to help it dry.

But if your engine is kept on your boat you will have to weigh up your options.  

You can either let the leg stay in the water, risking freezing and corrosion, or you can tilt the leg out of the water, which might trap the leg, leading to freezing and cracking. 

To store the battery you need to disconnect it from the boat otherwise, the low charge and chilling temperature could kill the battery entirely.

The best method would be to take the battery home and charge it up every now and then, this will keep it strong and kicking! 

Now your outboard motor is ready for its hibernation!

If this process seems too daunting to do by yourself, then a service engineer would be able to help you out.

But once you know what to do, the process is easy.