Why a simple bucket of fresh water is the secret to making a small outboard engine last

Stu Davies

If your outboard engine is struggling with salt build-up, follow these essential maintenance steps to keep the cooling channels clear

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Good preventive outboard maintenance should stop the build-up of salt and other deposits in the cooling system of a small outboard engine in the first place. Running it in a bucket of fresh water after use flushes the salts out.

My little 2.5hp Mercury is 20 years old and when I stripped it a few months back to change the main bearings, the cooling water channels were clean – probably because I do run fresh water through it on a regular basis.

However, I have seen badly blocked systems and the only answer is to take it apart and physically clean out the channels with a wire brush.

I am, of course, also aware of chemical products such as Rydlyme which can be used to flush through while the engine is running.

The inside of an outboard engine

With a light scrape and clean-out with a rag, the water passages are even cleaner. Credit: Stu Davies

The Rydlyme website says the product is non-corrosive and will not erode, pit, oxidize or have other detrimental effects on materials such as iron, copper, fibre, rubber, steel, plastic, brass, ceramics, glass, titanium, nickel, stainless steel and other materials associated with water-based equipment. No mention of aluminium, though.

So I asked about the aluminium castings used in our small outboards and the Rydlyme rep said that it was okay to use it, but not to leave it too long in the engine before thoroughly flushing it out.

Basically, put your Rydlyme mix in a bucket, take the propeller off and run the engine with the leg submerged in it to circulate it through the cooling system.

I’d be inclined to leave it no longer than a couple of hours before flushing it all through with clean, fresh water.

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