Is black smoke a problem ?

[dockmaster]

I am in the process of buying an old yacht with an 8 horse inboard yanmar before handing over the dosh I have insisted that I hear the engine running so today we conected a hosepipe to the raw water inlet and fired her up bearing in mind she hadnt been started for a while she started ok and sounded fine but lots of black (not blue) smoke which would eventualy disapear when the motor was run up but returned every time I gave her high revs - I dont think this is a big issue what do you think ?

 

[tinkicker0]

I take it the engine is a Yanmar diesel?

Could be a simple clogged airfilter issue or an injector / pump problem.
Black smoke is a big issue, apart from you sucking lungfuls of carcenogenic soot, an injector which is hosing could well wear out the rings and cylinder, or even erode the top of the piston.

A pump which has a stuck excess fuel device will entail removal of the pump and an overhaul to do the job right.

Check the fuel filter for water. Nothing scores an injector needle better than saltwater.

Have the owner put it right before parting with the wedge.


I take it you wern't just throttling up and letting her die away?

The very unsophisticated diesels often fitted in marine applications will often black smoke under hard accelleration, then once the governer has caught up and is metering the injection correctly for the RPMs, the smoke will clear.

 

[steve28]

its not a problem it is just unburnt diesel because the engine has no load, mine does the same and i was told by the yanmar agent that it is perfectly normal, i even had the injectors serviced anyway which made no diffrence at all.

 

[robmcg]

Is it a Yanmar YSE/YSM engine. If so no need to worry. They suffer from carbon build up in the exhaust bend which belches out loads of black stuff. Steve28 is quite correct here, will black smoke under no load. Generally, if it started OK and doesn't belch out blue smoke you are probably OK in this instance.

 

[dockmaster]

Not sure if it is a YSE/YSM I will check tomorrow but it is good to know the forum has the experience to help thank you

 

[savageseadog]

Is black smoke a problem ?
Yes, when you're voting for a new Pope

 

[dockmaster]

Sorry dont get it ??

 

[Spyro]

I would have said black smoke under no load is a problem. It's more likely to smoke when overloaded i.e. over propped dirty prop, dirty hull. You are obviously running this out of the water so presumably not in gear and not under load. I would not expect to see black smoke. As others say a common problem with these engines is the exhaust mixing elbow being blocked or worse completely corroded. From your previous post you said the tank was on top of the engine, this would make it a YSE8 which will be more than 30 years old. They are reliable and run for ever on a gallon of diesel but being a single cylinder horizontal bore they do vibrate and thump quite a bit.
Don't know if you will be getting a survey but you should check engine mountings. There are no longer available I had to replace mine (YSB8) and it involved removing the engine as the feet had to be drilled to take the larger diameter bolt on the new mountings. I would ask the seller to get the smoke problem fixed or offer a good bit less than the asking price.

 

[brianhumber]

Black smoke is incompletely burnt fuel in the form of small particles. Some older engines did not run very well due to lack of air at tick over so smoked on idle. However black smoke on load at revs indicates either a dicky injector, fuel pump or problems with higher loads coming from the prop/gearbox train on the engine loading more than the engine can produce from an incorrect prop pitch etc

On old engine could be just general wear and thus exhaust has sooted up. How often will you be at full power anyway. I would investigate further howeer.

White smoke no smell - water vapour think blown gasket
White smoke fuel smell - think vapourised uncombusted fuel
Black smoke - not fully combusted fuel -
Blue smoke - think oil and worn engine

Faint dark haze - think life is good

 

[Iota]

white smoke = new pope
black smoke = deliberations ongoing

or something like that
/forums/images/graemlins/smile.gif

Iota

 

[dockmaster]

Sometimes life is tough already knocked him down 1500 quid then insisted on 2 batteries and charger dont think I will get away with any more !! the engine was rebuilt in 2000 hasnt been used in the past 2 years is easy to remove and work on but i dont know if spares are still available.

 

[JAYEL]

Overhauled my Trappers YSB8 last season ,it was using lots of oil, black smoke under load when the boat reached max hullspeed. New gaskets throughout New rings, New Exhaust Elbow and Recon Injector, including VAT £360, a couple of new hoses and reground valves. Runs like a dream.

 

[dockmaster]

OK that is good enough for me problem solved !
where do you get your spares from?

 

[JAYEL]

Speak to Cellar Marine on 01326280214 down in Cornwall, they now Yanmars inside out,are very helpfull, are cheap and can supply by next day post. Can't speak too highly of them

 

[dockmaster]

Once again thanks for all your help.

 

[Burnham_Bob]

Had the same problem with a yanmar 8hp in boat I was buying. The engines date from the time when a diesel was well and truly an auxiliary for getting on and off moorings and into harbour. The 8hp wasn't really man enough to push you through a headwind and a rough sea. The one in the boat I bought threw out clouds of black smoke and wouldn't develop full power. The engineers recommended a full top end overhaul but in the end we did a deal and re-engined with a bigger diesel

Have you done a sea test in rough weather? There is a chance that if you run it and blow all the crap out of it it might get better.