How do you fix a smoking 2-stroke boat engine?
Whether you sail on a speedboat, an inflatable boat, a semi-rigid, a yacht, a fishing boat, a sailboat or even a dinghy, we are all afraid of an engine failure at the most delicate moment. So when we see his 2-stroke boat engine smoking blue, white or black, many of us are not serene! The causes can be multiple depending on the type of smoke. Indeed, there are 'normal' smokes and then there are problematic smokes... Before panicking, read this guide which explains how to fix a smoking 2 stroke boat engine. Sometimes the smoke is not an alarming sign, sometimes the problem is very simple to solve, and then sometimes it is much more complicated… In this article, we first describe how to analyze the smoke coming out of your engine marine. Then, we detail what are the possible causes of this malfunction depending on the type of smoke (blue, white or black). And finally, we share the solutions to implement to repair your 2-stroke boat engine depending on the causes.
When is it normal to have a smoking 2-stroke boat engine?
Analyzing the fumes coming out of your marine engine is a good thing. Indeed, the smoke from a 2-stroke boat engine is the first visual cue to detect damage. But not all fumes are cause for concern. You must therefore be able to distinguish in which cases is it normal to have a smoking 2-stroke boat engine. We have listed all the 'normal' situations below:
- Smoke comes out of my old marine engine
If you inherited a 2-stroke boat engine from 1990 or older, then it's normal for it to smoke.
- Smoke comes out of my outboard motor when starting
It is common to see a 2 stroke outboard motor smoking when the engine starts. Do not worry: it is only water vapor that forms at low pressure when the outboard motor is idling! However, if the smoke doesn't dissipate within minutes, then you have a problem.
- Smoke comes out of my two-stroke fuel-injected outboard when I just bought it
If your fuel injected 2-stroke outboard is new, then it may be smoking. Indeed, during the first outings at sea, the electronic control system will inject more grease than expected into the boat's engine. This temporary over-greasing is necessary so as not to damage the cylinders of the outboard. As a result, during this 'break-in' period there is a good chance that your 2-stroke boat engine will smoke.
What Causes a Smoking 2-Stroke Boat Engine?
To determine which are causes of a smoking 2 stroke boat engine, it is necessary to analyze the color of the smoke. To do this, you have to start your 2-stroke engine and wait for it to warm up. Indeed, the fumes of a cold engine do not provide any clues. These start-up fumes can be very dense and black, but they are normal. Once the 2-stroke boat engine is at full throttle, the initial smoke should be gone, giving way to colorless, odorless exhaust. This gas may turn gray when accelerating. It's normal again. But if the smoke persists for several minutes at cruising speed, then your 2-stroke boat engine has a problem. It exists 3 colors of smoke possible on an outboard or inboard motor : white smoke, blue smoke and black smoke. You should be able to easily determine the cause of the malfunction once you know the color of the smoke.
NB: the causes are the same on all brands of marine engine : Yamaha, Mercury, Suzuki, Johnson, etc… And whatever the power of your 2-stroke engine: 6hp, 15hp, 25hp, 30hp, 50hp, 60hp, 75hp, 100hp, 150hp, 250hp, etc…
What causes a 2-stroke outboard motor that smokes white?
A 2-stroke boat engine that smokes white is not a big problem. White smoke is a sign that the outboard motor is venting water vapor. There is nothing to be alarmed about but you have to solve the problem. The causes of a 2-stroke boat engine that smokes white are multiple:
- Water may have entered your tank. When the boat's engine burns your fuel, it converts this excess moisture into white smoke.
- Your engine's water circuit is scaled up. To cool, all boat engines use a water-fed cooling circuit. The scaling of this circuit produces overheating. By heating, the marine engine converts the water in this circuit into white smoke. In most cases, the problem comes from an obstruction of the water inlet by algae or plastic waste.
- Finally, the problem may come from a leak in the cooling circuit. If a seal is no longer tight then water will seep into the cylinder of the marine engine. When burning, this water will create white smoke. Even if the leak can come from any duct, there is a good chance that the problem lies with the cylinder head gasket.
What causes a 2-stroke boat engine that smokes blue?
A blue smoking 2 stroke boat engine is a sign of a lot of oil in the combustion chamber. This is because the oil produces blue smoke once it burns. There are several possible causes:
- You may have just done an engine oil change. The engine simply burns off the excess oil you added.
- There may be a malfunction with your injection system. For example, an injector no longer closes.
- Finally, the problem may be wear on the scraper rings or carbon buildup on the valves.
What causes a 2-stroke boat engine that smokes black?
A 2-stroke boat engine that smokes black is a sign of poor adjustment. The black color of the smoke comes from the soot exhaust. A marine engine produces soot when it does not burn its fuel properly, lacks combustion air or has excess carbon deposits. The causes of a 2-stroke boat engine that smokes black are multiple:
- Often, black smoke is simply from poor gasoline that is too rich for your marine engine.
- If the black smoke occurs suddenly while sailing, then the problem is an engine overload. Generally this overload of the motor comes from an obstruction on the propeller (fishing net, plastic waste, algae, ends, etc...). But it could also be that your boat is overloaded, that the hull is dirty or that your propeller is not suitable.
- Another possible cause is a problem with the injection pump. An injector may be incorrectly adjusted and send too much fuel into the combustion chamber.
- Finally, the black smoke from your 2 stroke marine engine could be a dirty air filter. This is particularly the case when black vapors appear on acceleration. When you rev up, the boat engine needs more air and with a clogged air filter the engine will choke.
How do you fix a smoking 2-stroke boat engine?
Solutions to repair a 2-stroke boat engine that smokes white
If your white smoked 2 stroke boat engine, you need :
- Check that your gas tank is not leaking. If so, move the tank and replace the fuel.
- Check that the water inlet is not clogged. If so, remove the cap.
- Check if there is a leak in the cooling circuit. Test the cylinder head gasket first. If it is no longer tight, replace it. (You will find many spare parts on Amazon)
If none of these solutions work, stop the marine engine immediately and contact a mechanic. He will be able to carry out a more complete examination of the situation and resolve your white smoke problem.
Solutions to repair a 2-stroke outboard engine that smokes blue
If your 2-stroke boat engine smokes blue, you need to check the oil level in the case of a recent oil change. Remove the excess oil with a drain pump and wait for the engine to burn off the excess oil already in the cylinder. There is nothing to worry about.
However, if the blue smoke persists and the oil level continues to drop, the marine engine should be stopped immediately. Indeed, without oil you risk breaking everything.
If the problem is not a too high oil level, you need to contact a mechanic. Only an expert can repair an engine wear problem. He will have to check the condition of many parts such as piston rings, valve seats, etc.
Solutions to repair a 2-stroke boat engine that smokes black
If your 2-stroke boat engine smokes black, you need:
- Check that nothing is obstructing the propeller. If so, all you have to do is free the propeller from the stuck fishing net or seaweed. A dirty propeller can also cause black smoke. You will have to put the engine in neutral and clean the propeller.
- Check that the hull is clean. If not, clean the hull (see a good special hull cleaner).
- Check that your propeller is suitable for your boat. If not, change it by following our guide: 'which engine to choose for my boat?
- Replace the gasoline in your tank if the problem appeared after refueling. The fuel is very likely to be either of poor quality or too rich.
- Check the condition of the air filter, especially if there is a loss of power when accelerating. If it is clogged, you will need to change it. Replacing an air filter is very simple - you don't even need a tool on most 2-stroke outboards. (You will find many spare parts on Amazon)
If your 2-stroke boat engine continues to smoke black after checking everything, then contact a mechanic. The problem is certainly with the injection and only an expert can calibrate the injectors correctly.
Conclusion on Smoking 2-Stroke Outboards
In summary, all boat owners should be aware of marine engine exhaust fumes. If the smoke does not dissipate after warming up the 2-stroke outboard motor, you have a problem. The color of the smoke is a valuable clue in finding the cause of the problem. We will remember :
- A 2-stroke boat engine that smokes white = water in the engine
- A 2-stroke boat engine that smokes blue = oil in the engine
- A 2-stroke boat engine that smokes black = adjustment problem (overheating)
White or black smoke coming from an outboard or inboard motor can often be fixed on its own. However, if your 2-stroke boat engine is emitting blue smoke, in most cases you will need to seek help from a marine mechanic.
Learn more about boat motors:
What gasoline to use for a boat engine?
