Bukh. Dv10 smoking

[lancelot]

I ran the engine today, after it had been idle for about 5 weeks. I usually run it for about an hour and a half once a fortnight. Today, there seemed to be a lot of smoke, white to light grey in colour, very unusual as I have never noticed it before. Water was also being pumped out as one would expect, so the raw water system appeared to be working OK. Increasing revs also increased the smoke emitted. The engine sounded OK. and ran happily for the planned hour and a half.
The engine has worked fine for years. Why would it suddenly start smoking?
The engine is about 30 years old and serviced regularly.
I was wondering if the use of diesel treatment has anything to do with it. I have been using the stuff for several years.
Other thoughts were oil seals, piston clearance etc. and a cold wind making it look worse than it it (wishful thinking).
My worse fears are of reconditioning or replacement.
Any advice would be appreciated. Oh yes, the boat is a much loved Cobra 850, mature but reliable.
Fair winds,
Lancelot

 

[Rossynant]

"Suddenly' sound suspicious. White may mean water in engine. Possible? Check the oil for this anyway, might be milky. Engine with water inside will run as usual. But will suffer corrosion.

Hard to say what someone else see as white or light grey, or light blue...
Oil burning would be indicated by smoke looking rather bluish, more at higher load (revs unimportant). But should not be 'suddenly a lot' - unless something serious happened to the engine, which would be noticeable beside the smoke.

 

[vyv_cox]

Was this at Milford Haven, pontoon C?

Bukh engines are renowned for steaming, as I'm sure you are aware. It was fairly cold on the day, which would perhaps make steam more visible. Otherwise, light coloured smoke usually indicates a fuel problem such as an injector not spraying correctly but it is usually accompanied by a strong smell of diesel.

Rossynant's suggestion of water in the engine is worth investigating. Bukh water pumps have something of a reputation for seal failure, allowing water into the engine. See some dramatic photos on my website. Suggest you look fairly soon just in case, before corrosion seizes the piston to the bore.

 

[oldharry]

I ran the engine today, after it had been idle for about 5 weeks. I usually run it for about an hour and a half once a fortnight.
Other thoughts were oil seals, piston clearance etc. and a cold wind making it look worse than it it (wishful thinking).
My worse fears are of reconditioning or replacement.
Any advice would be appreciated. Oh yes, the boat is a much loved Cobra 850, mature but reliable.
Fair winds,
Lancelot

I usually run it for about an hour and a half once a fortnight. Down the Cleddau I hope! Nothing worse you can do to an engine than run it off load , and this could well be the root cause of the smoking, if that is what it is. Diesels MUST be worked reasonably hard or all kinds of problems can arise, particularly in a direct cooled engine which even in 1.5 hours will not warm properly through unless it is working reasonably hard. Leaking head gasket or even cracked head is not unknown with this sort of treatment.

Or it may just have been a cold day making the normal steam more visible. My DV20 even on the hottest day would always trail a wisp of steam, and in winter there was always poor visibility looking aft!

 

[lancelot]

I usually run it for about an hour and a half once a fortnight. Down the Cleddau I hope! Nothing worse you can do to an engine than run it off load , and this could well be the root cause of the smoking, if that is what it is. Diesels MUST be worked reasonably hard or all kinds of problems can arise, particularly in a direct cooled engine which even in 1.5 hours will not warm properly through unless it is working reasonably hard. Leaking head gasket or even cracked head is not unknown with this sort of treatment.

Or it may just have been a cold day making the normal steam more visible. My DV20 even on the hottest day would always trail a wisp of steam, and in winter there was always poor visibility looking aft!

Thanks for the suggestions guys. Yes, I always run the engine loaded - into gear once it is warm and left tugging the pontoon. Run it hard for about 90 mins.
The oil does not show any sign of contamination (milky) I checked that. On the DV10 I had the water pump reconditioned with a new spindle approx. 2 seasons ago. There does not appear to be any water leaking into the engine from the water pump system.
The engine compartment has a 60W. tubular heater to keep it frost free. I assume it did not freeze when it was idle.
No it was not in Milford, rather Swansea.
Thanks anyway, perhaps I should look for medication for my paranoia.
Fair winds,
Lancelot

 

[lancelot]

Thanks Viv. Your website is excellent - much food for thought.
Fair winds,
Lancelot

 

[LittleSister]

Could someone explain the Bukh's steaming a bit more, please? We've recently acquired a boat with a DV10 and I want to know what I'm looking at/for. Our's is indirectly (freshwater) cooled with a Bowman heat exchanger, so maybe it doesn't apply?

 

[Rossynant]

May not apply. It was typical on direct cooled, just the way they are made. Probably water left the engine quite hot. Bukh is a nice machine (or the king of engineering I like) robust, tolerant. But compared to some modern ones may be seen as unusual in some aspects, complicated. It was an example in lectures on engine design
I'm not sure of this really, but what comes to mind:
Seawater pump in them was bit small, may have problems with installations where its not easy to draw this water for some reason (small piping, filters, engine high above waterline). New models were fitted with new kind of pump, I heard this is better.
Inlet into engine block (from pump) was easy to get blocked with salt/scale - mostly as engine gave no problems, so nobody bothered with maintenance Sometimes also exhaust elbow was blocked or corroded, getting too hot.
This is tip for OP: check, may be there is a build-up of scale inside the engine after all those years. Not necessary now, as oil is OK, but if it persist.

Anyway lots of steam, as may seem to the eye, may just be a steam which is always there, just happened to condense on chilly day with 100% air humidity. Winter after all...

 

[vyv_cox]

Could someone explain the Bukh's steaming a bit more, please? We've recently acquired a boat with a DV10 and I want to know what I'm looking at/for. Our's is indirectly (freshwater) cooled with a Bowman heat exchanger, so maybe it doesn't apply?

I have no experience of an indirectly cooled one. It is likely that the steaming problem would not occur. The injection point for seawater, behind the flywheel, is always problematic for fouling, which restricts water flow into the block. The seawater flow rate is quite small anyway, my DV20 had a 1/2 inch seacock which is quite small by current standards.

 

[lancelot]

Cheers guys.
I will recheck the impeller blades, just in case one has broken and is reducing the raw water flow. I did renew the impeller last summer during the engine service.
Fair winds,
Lancelot

 

[vyv_cox]

Check the injector behind the flywheel. It is held on with two allen screws, awkward to undo but it can be achieved without removing the flywheel. The design of the thing is like an old fashioned gas poker, a closed tube with many drilled holes. These frequently become clogged with calcium salts and need to be cleaned out.

 

[lancelot]

Check the injector behind the flywheel. It is held on with two allen screws, awkward to undo but it can be achieved without removing the flywheel. The design of the thing is like an old fashioned gas poker, a closed tube with many drilled holes. These frequently become clogged with calcium salts and need to be cleaned out.

Cheers Vyv.
I will have a look asap.
Fair winds,
Lancelot.