Winterising a boat motor: fact or fiction?

RACV Marine

Boat engine

Easter marks the end of the boating season for many Victorian bread and butter fishermen. Snapper season is ending, winter is just around the corner, gear goes into storage and those long-overdue maintenance tasks are (finally) about to get done.

All good boaters know that preventing corrosion is an essential part of boat ownership. Proper and regular maintenance stops things from breaking or failing which is why winterising your boat — and especially the motor — is such a vital part of your maintenance routine.

Or is it?

Who should winterise?

“The more you use your boat, the better it will be,” says Nick Purvis from Coastline Marine. “If your boat gets regular use during winter, then you don’t necessarily have to winterise it,” he says.

Nick certainly knows boat engines. A marine mechanic for 15 years, he operates near Patterson Lakes and Sandringham Yacht Club. The engines he sees each day range from portable recreational outboards to big commercial diesels — and he says the best way to prevent an engine from deteriorating is to keep using it.

“On recreational boats, if you can use it once a week or fortnight, then you’ll certainly prolong its life,” he says. “Even something as simple as a quick run will do it a world of good.”

Of course, not everyone is able to keep going during the coldest and darkest months of the year. Work, weather and a lack of holidays can get in the way, so unless you’re fortunate enough to head to Portland or some other gamefishing paradise, keeping your boat in working order by placing it in hibernation may be the best option.

Winterising a marine engine

The engine is the component of your boat that is arguably most at risk of deterioration over winter. After all, not only does it contain many moving and (often delicate) parts, it is also routinely subjected to salt water immersion and high temperatures. However, winterising can mean different things to different people, as Nick explains.

“It really depends on how in-depth you’re getting into it,” he says. “For some people, a winterise is just running the boat up on fresh water, packing it up, isolating the batteries and giving everything a bit of a spray with CRC. They’ll do the basics and call that winterising.”

Nick concedes that, when it comes to maintaining his personal boat, the lengths he goes to are considerable. “Most people probably wouldn’t do all the individual things that I would do for my own boat,” he says — but then again, he is a professional marine mechanic.

For the rest of us, here are some basic steps to get you started for winterising a recreational marine engines.


Always read the manual

Regardless of whether it’s an outboard or inboard or sterndive, the key to winterising a boat motor is to always follow the manufacturer’s recommendations. If you think your mechanical aptitude isn’t quite up there, seriously consider enlisting a professional.

Run it with fresh water

“The engine needs to be run with fresh water, ideally with an additive like a neutralising agent,” says Nick. “You want to get rid of salt water or any salt build-up in the engine prior to it going into that layup period. It’s important to run it up to temperature, as this ensures that thermostats and other components have opened.”

Nick cautions that it’s important to do this thoroughly, even if the engine has received minimal use.

“We’ve had engines that have been very clean externally, but which have had severe internal corrosion because they weren’t flushed properly. This was despite the fact that they’d been used just two or three times over the summer,” he says. “Salt inside the water galleries will, over time, corrode the inside of the block.”

Fog the engine

Fogging, if you’re not familiar with it, is the process of creating a protective barrier inside an engine’s internal components by applying an oily layer. There are different kinds of fogging oil on the market and, depending on the engine, you would likely spray that into the throttle body to draw the fogging oil into the engine (again, read the instructions).

This coats a lot of the internal parts of the engine with a light oil, which acts as a barrier against moisture. It’s a particularly important step for boats kept in open areas with a lot of salt in the air (e.g. near the beach).

“As you spray the fogging oil into the engine intake, you would try to stall it on that oil. The engine becomes ‘choked’ whereby the parts in the air intake system get coated, all the way through to the individual cylinders. Normally, the air intake system only has air passing through it. By adding fogging oil, you coat the internal parts, which protects the engine from cold and wet air,” he says.


Spray it with corrosion protection

With the engine having been run, it’s time to coat it with a corrosion protection spray. If it’s an outboard, remove the cowl and spray the components with a protectant, like a water dispersant. Like the fogging oil, this creates a barrier that protects against rust.

The process is similar on an inboard or sterndrive. However, you should also coat the transmission and the sterndrive components. Once more, follow the procedures recommend by the manufacturer.

Grease cables and moving parts

Apply a grease to the cables and other moving components. “That puts a coating on all those parts which keeps everything lubricated if the engine isn’t going to be moved during the layup period,” says Nick. “Work the steering back and forth to make sure that those moving parts get a final check. Give it a final bit of grease and lube up those points.”

Isolate boat batteries

Dead batteries and contaminated fuel (see below) are the two most common reasons for Coast Guard callouts immediately after winter.

Though not specifically an engine component, batteries are obviously vital to keeping your engine working, so look after them when they’re not in use. Isolate your battery switches. Turn them off or, if your boat doesn’t have a battery switch, consider disconnecting your batteries. RACV Marine’s guide to marine battery maintenance has many handy tips.

Fuel management

Several stabilisers and additives on the market can help preserve fuel quality over winter. Even so, the age-old question of whether to fill the tank to near-full capacity or drain it continues to divide people.

“Some people say you should always run your tanks full to avoid condensation. Some people say they should be run low,” says Nick. “I recommend that if you treat the fuel that’s in there then that fuel may be alright for the next use. However, I strongly recommend filling it up prior to the next use.”

While you’re at it, it’s a good idea to inspect and drain any water-separating filter, if these are separate (or even consider installing them).


Oil change

As a general rule, oil tends to deteriorate only with use, so it’s good practice to perform an oil change after a lay-up period. This way you will know whether you have fresh oil in the engine. Periodically noting the condition of engine oil is also good practice.

Obviously you should use the oil recommended by the manufacturer.

Pay less for your marine insurance

Last but not least, if you know your boat is going into hibernation, why not pay less for your boat insurance? One option is lay-up cover. Quite simply, nominate the period for which your boat does not get used. You then pay less on your monthly premium during this time. Visit RACV Marine to find out more about lay-up insurance or call 13 72 28.

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