Black sooty muck from my exhaust

[WayneS]

I'm sure that this has been dealt with in the past but here we go again.

A couple of weeks ago I managed to overheat my single cylinder diesel (Farymann 12Hp) but because some duffer (well, me actually) managed to screw up the refit of my water pump.

As a result of the overheating I had to replace the flexible exhaust as well.

Over the week-end we gave the engine it's first thrash since this episode and I noticed and increased amount of black smoke when she was under load and also what looked like soot mixed with the exhaust water.

Have I done some damage to the lump or is it just cleaning itself out.

Any advice would be appreciated.

Cheers

Wayne

 

[dickh]

This is usually a sympton of unburnt fuel. Check your exhaust elbow(where the cooling water is injected) to see if it is blocked up, thereby causing back pressure. Then check injectors and finally fuel pump - but if it was running OK before your overheat then these are unlikely.


dickh
I'd rather be sailing...

 

[Guest]

If by "overheat" you mean "it seized up and stopped" then it could be that due to damaged piston rings you are not getting complete combustion and you may also be burning a lot of oil. Check out the compression ratio and oil consumption.

If by "overheat" you mean "it was running hot when I stopped it" then you could be lucky and it has done a "self de-carb". In which case it may be cleaning itself out and I agree with the previous post to check out the exhaust first and if that doesn't seem to be the problem then check the injectors.

Hope you were lucky.

Best regards )

Ian D

 

[Chris_Stannard]

I was advised by the Yanmar technical team to run my engine at full power for about 20 to 30 minutes every ten to fifteen hours. Local diesel mechanic, who I trust agrees saying this clears the carbon off the exhaust valves hence the exhaust during this period may be thick with soot. Other advice is to build up to full power over a period of about 10 to 15 minutes and slow down the same way to reduce thermal stress and shock in the engine.
It may be that if you have not run at full power for some time this is what you have achieved and the soot was the carbon from the exhaust valves. If your engine is now functioning normally, and you have had a good check round, it may well be okay.

Chris Stannard

 

[terence]

hi chris no you should never ever run a yanmar at full pelt because bieng a yanmar single potter if you look at the top of the engine there is a fuel return pipe any unburn diesel is just returned to the exhaust water outflow ? only ever run your yanmar at 3/4 max power good boating terry......stop

 

[dickh]

Surely the fuel return pipe MUST run back to the fuel tank- I've never heard of it being run to the 'exhaust water outflow' - this means you will get fuel sent straight overboard!!

dickh
I'd rather be sailing...

 

[Robin2]

I agree. All diesels have a fuel return pipe to the tank. The Yanmar maximum power rating is based on full power for 1 hour - the constant speed power is somewhat lower.

 

[david_bagshaw]

Could be a bit of the old exhaust pipe burnt off? broke off & has lodged in the exhaust system lower down causing back pressure & poor combustion.

or

the carbon & muck near the seawater injection point got hotter than usual & has expanded & restricted the exhaust at that point also causing pressure & poor combustion.

If it didnot black smoke before under full load and does now, there is definately something wrong. just check there is not a bag on the prop that has been picked up at the same time.

one last thought, in the repair have you had the air filter/collection system off, may be it is not back on properely.

good luck

David
www.euroboating.net