Question 1

What is the most likely cause of continuous black smoke from the exhaust of a marine diesel engine?

Accepted Answer

Incomplete combustion of fuel.. Black smoke consists of unburnt fuel particles (soot). This is a sign of incomplete combustion, often caused by overloading the engine, a dirty air filter, or faulty/dirty fuel injectors.

Question 2

The engine exhaust is emitting blue or blueish-grey smoke. What does this typically indicate?

Accepted Answer

The engine is burning lubricating oil.. Blue smoke is a characteristic sign that engine lubricating oil is entering the combustion space and being burned with the fuel. This may be due to worn piston rings, cylinder bores, or valve stem seals.

Question 3

What is the most serious cause of dense white smoke (steam) from the exhaust of a warm engine?

Accepted Answer

Coolant leaking into the combustion space during engine operation.. Coolant entering the combustion space is the most serious cause among these options. It may result from a failed head gasket or a crack in the cylinder head or block. However, dense white exhaust from a warm engine is not necessarily steam: unburnt fuel can also produce white smoke. In a marine wet exhaust, excessive steam can indicate insufficient cooling-water flow, so its appearance alone does not establish that coolant is entering the cylinders.

Exhaust Smoke Colour Diagnosis, questions and explanations

What is the most likely cause of continuous black smoke from the exhaust of a marine diesel engine?

The engine exhaust is emitting blue or blueish-grey smoke. What does this typically indicate?

What is the most serious cause of dense white smoke (steam) from the exhaust of a warm engine?

Practise this properly

Exhaust Smoke Colour Diagnosis, questions and explanations

Questions

What is the most likely cause of continuous black smoke from the exhaust of a marine diesel engine?

The engine exhaust is emitting blue or blueish-grey smoke. What does this typically indicate?

What is the most serious cause of dense white smoke (steam) from the exhaust of a warm engine?

Practise this properly