What can the colour of your outboard engine smoke tell you?

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If your outboard engine smoke is not its usual colour, it may signal a problem. Reach out to your local mechanic to diagnose the issue.

White smoke may mean water or vapor. “Usually, white smoke is a sign that the engine is running hot,” says Kevin Dault, of Maple Leaf Marinas. If the engine isn’t getting enough water for cooling, the remaining water will evaporate, producing a white colour. It could also indicate a water leak in the cylinder head or gasket.

Blue smoke is a result of burning oil. This is normal in older two-stroke engines that run on a fuel-oil mixture, but in newer engines “this could be a sign that the engine was overfilled with oil or that the engine is just getting worn out,” says Dault.

Black smoke can be a sign of overfuelling or a “rich” fuel-air ratio. The engine is designed to burn a specific mix of fuel and air and too much fuel can cause the engine to run rough and produce black smoke. According to Dault, there are many possible causes, including a stuck-open fuel injector, a malfunctioning fuel pressure regulator, or a defective carburetor float.

This was originally published part of the article, “Secrets of the Outboard Whisperers,” in the Mar/Apr 2022 issue of Cottage Life.

Read more: Outboard engine trouble? Advice from the experts

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