Analyzing Smoke Coming From Marine Diesel Engine

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Along with the problems you can identify from gauges and testers, the smoke emitting from marine diesel engine exhausts can also warn you of potential problems.

In this blog post, we highlight the various types of smoke and what they could mean for your engine.

Here are the different types of smokes you might encounter and what they really mean:

Dark Black Smoke

Black smoke coming from the diesel engine exhaust could indicate unburned fuel. This is typically due to an overload. When too much fuel is poured in—more than the engine can easily burn—the engine is gunned and emits a gust of black smoke.

A constant stream of black smoke when the engine is running or under load means that it is being continually flooded with fuel it can’t handle.

This could mean that the propeller on your engine has a larger span or it has too much pitch. In many cases, the propeller is problematic. In fact, a few barnacles could also lead to this issue. Also consider inspecting air filters and injectors.

Blue Smoke

Blue smoke typically indicates that oil is being burned in the engine compartment. This also leads to carbon buildups. Worn out guides or valve stems may let engine oil seep past and mix with the diesel fuel. As oil is much heavier than diesel fuel, it doesn’t burn. As a result blue smoke is formed.

Determining the problem might be difficult here. Is it the guides or valve stems or is it the piston rings calling for a cylinder leak down test? There could be a number of reasons. Consider heading to the boatyard.

White Smoke

White smoke is one of the most complicated problems to figure out. It could either be due to a piston ring blowby leading to poor combustion or it the engine could be overcooled, maintaining a temperature where appropriate combustion is not possible.

While white smoke is normal when an engine is fired up, it can be a problem if it persists. In cases where the intake heater malfunctions, the white smoke may persist longer. Also consider checking the fuel quality if you notice this type of smoke.

White smoke may also emit due to a blown head gasket, inappropriately adjusted valves, or even a cracked cylinder.

Most of the marine diesel engine problems can be avoided simply by practicing proactive maintenance. Get in touch with us for a collection of high quality marine main engine parts to keep your engine healthy and running at all times.


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