White smoke

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At the start of the season I moved my boat fromt the Blackwater to the Clyde. The engine (a 3 cylinder Yanmar) was fine at the end of last season and was winterised and recommissioned for me prior to the move. It now emits white smoke - an initial burst on starting, then nothing until it has warmed up but produces copious amounts cruising at 2000 revs.

First thought was water in fuel, but water trap OK, and no signs of cylinder head gasket problems - internal coolant level OK and oil looks fine. My local marine engineer recons it is just to do with the colder sea water giving a similar effect to a car exhaust on a cold day. However I'm not convinced and the Clyde does not feel significantly colder than the North Sea to me.

Any thoughts or suggestions. The engine seems to be running OK but I don't want to just ignore what might be a problem.
 

ahab

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My immediate reaction would be that the engine is running colder due to the drop in the ambient water temperature. I have a Sabb 2 cylinder diesel and I have been surprised at the difference made by small changes in water temperature.

What do your guages tell you? Is the engine running cooler?
 

AndrewB

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\"No signs of a cylinder head gasket problems\"?

Did you actually check? This sounds like a classic cylinder head problem, specially if it appears at increased revs. Not all head problems are visible on the outside.
 
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I experinced a similar problem. Under gentle revs, less than 2000rpm, the exhaust looked fine, but as soon as I increased power white smoke would blow out.
Coming into the marina a friendly mechanic saw the problem and asked me to check the cooling intake filter. Lo and behold, the filter was covered in an algal slime, and once cleaned the engined performed OK. Apparently, the slime inhibited the throughput of water at high revs, but was alright when the engine was running gently.

Might be worth checking.
 

AndrewB

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But ...

... if you had a raw water intake blockage, wouldn't the white smoke signify that your cooling water was nearly boiling? Was your engine showing signs of overheating? I would have expected the alarm to be going.
 

brianhumber

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Suggest before you start ripping the head off, check the basics. Are you getting plenty of water coming out of exhaust. Has a blade off the SW pump been ripped off and lying across HE tube plate.
Is change in ambient SW causing the thermostat to operate at a different temperature? etc etc
 

oldharry

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There are two sorts of white smoke a boat engine can produce: by far the most common is steam, as your engineer suggested. Causes already discussed on this thread, but like the others I strongly suggest you check your cooling system through thoroughly before you start ripping the engine apart.

The other cause of white smoke is when the engine fails to burn each fuel charge fully, and passes unburnt atomised fuel into the exhaust appearing as white smoke, and is very often seen on cold start when a preheat plug has failed. It can be caused by a range of injection problems or low compression from damage, wear, or gasket failure. The mechanical aspect is easiest checked by having a compression test done. If compression is up to spec, then the engine itself is probably OK, and you need to start looking at the injection system: cold start mechanism operating correctly? Pump timing correct? Injectors need servicing or resetting? Injector pump fault? Have you replaced any of the injector pipes - if so are they the correct bore? Most of these injector faults require specialist equipment and attention to find and cure.

Slight air leaks in the low pressure fuel line between the lift pump and the injection pump are a very common cause of white smoke - look for bubbling joints. Joints must be absolutely dry. The low pressure line actually goes to negative pressure each time the injector pump operates particularly at higher speeds and a stream of tiny air bubbles is sucked in, not enough to stop the engine, but enough to upset carburation and produce white smoke, particularly at speed.

But before you go in to all that - check and double check your cooling system. If the engine was Ok before, its unlikely to be anything other than the minor cooling problem suggested by your engineer.
 

saltydog

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Due to the Gulf Stream I would be surprised if sea temp a problem ... I once managed to stuff my lockers so full tht the engine was gasping = white smoke.
Also my Yanmar has had new cylinder head gasket .. it managed to work for quite a while .. I was lucky not to bend a con rod ...in my case starting was a bit slow, then it ran OK for a while... eventually it was not developing power
 

Colvic Watson

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But before you go in to all that - check and double check your cooling system. If the engine was Ok before, its unlikely to be anything other than the minor cooling problem suggested by your engineer.

I know this is an old thread but shows how great the forum is. Tonight we were motoring down the Deben, suddenly lots of white smoke from the exhaust; thoughts of blown head gaskets and blocked injectors. Moored up PDQ and google searched the forum and came up with this thread - so we took the cover off the water strainer and a piece of clear plastic was in there blocking 50% of the intake. So thanks everyone who contributed and oldharry who I've quoted.

All cleaned up and no smoke. A bit more relaxed now!
 

pagoda

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;9748 said:
At the start of the season I moved my boat fromt the Blackwater to the Clyde. The engine (a 3 cylinder Yanmar) was fine at the end of last season and was winterised and recommissioned for me prior to the move. It now emits white smoke - an initial burst on starting, then nothing until it has warmed up but produces copious amounts cruising at 2000 revs.

First thought was water in fuel, but water trap OK, and no signs of cylinder head gasket problems - internal coolant level OK and oil looks fine. My local marine engineer recons it is just to do with the colder sea water giving a similar effect to a car exhaust on a cold day. However I'm not convinced and the Clyde does not feel significantly colder than the North Sea to me.

Any thoughts or suggestions. The engine seems to be running OK but I don't want to just ignore what might be a problem.

I have a 3 cylinder Yanmar which had similar behaviour. More obviously when it was cool/cold, but generally when the engine was working quite hard. White exhaust, which was mostly steam. No obvious alarms. It is a raw water cooled engine.
I took the head off and the thermostat housing. Gaskets were OK. There was a fair quantity of "calcified" deposits in the head and block narrow water passages,so I cleaned out what I could manually and re-fitted the head with new gaskets.
Once running, I filled a bucket with a mix of patio cleaner & vinegar, and let the mixture work it's way round the engine (bucket positioned to catch the discharge).
I let it soak for about 20 minutes and it frothed mightily as the carbonates were removed by the dilute acid. After it was back on seawater, the steam problem has since gone away entirely. Just a hint of normal diesel exhaust occasionally.
If you have a heat exchanger you might have similar deposits collecting in there, though this is more of an issue with raw water cooling. Most of the crud was in the exhaust manifold, where the water exits a hole in the casting to go up & out into the elbow.
Yanmar gaskets ain't cheap, but it was a useful excercise pulling the head off and checking things out.

Graeme
 
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