Volvo TAMD41HD Low Revs and Black Smoke.

[nigelstgeorge]

Posted on behalf of my Brother in Law.

His boat an HR53 is fitted with a Volvo TAMD41HD and based in Langkawi, Malaysia. Major issue with low revs when cruising and black smoke>

In the normal low gear, the turbo kicks in at around 1700rpm and cruising revs are from 1800-2200. In the overdrive gear, the turbo kicks in at around 1450 revs and normal cruising revs are 1500-1700.

If I run the engine in the high overdrive gear, the engine runs fine with no black smoke up to 1250-1300 revs, thereafter the black smoke increases with increasing load. It is not so bad in the normal low gear, but a similar pattern emerges when the engine is under load. In neutral, there is little to no black smoke.

WORK CARRIED OUT

1 Full engine service
2 Fuel tank cleaned out (it was quite dirty)
3 Fuel lines to engine cleaned
4 Racor filters and air filter replaced
5 Fuel float replaced (old one was probably ok)
6 Injectors serviced (no problems reported)
7 Turbo cleaned (it is spinning ok) but I cannot pressure test it in Langkawi.
8 Exhaust elbow riser has some serious corrosion (only 2 years old!) and needs to be replaced but is still functioning ok. There is no sign of eloctrolisis.
9 Prop cleaned thoroughly with no malfunctions/obstructions. Gear mechanism and blades rotating freely. No sign of any prop damage.

THE PROBLEM

The problem is obviously too much fuel and/or not enough air getting in, but there has been no improvement from any of the above actions. From our engine tests in the marina tied up against the pontoon, we have found the following:

1 We cannot get the revs above 1300rpm now in the overdrive gear. With full throttle, the revs start to die and the back smoke and raw soot/fuel is excessive
2 We have however just established that the engine will run smoothly up to 2,400 revs in reverse with no black smoke. So the problem seems to be only in the 2 forward gears which would imply a gear box, prop shaft or prop problem? This test was not done at any previous time.


(PS I have now has 3 risers: the first one which lasted 6 years, 1 which lasted only 18 months and this one which has not been used much but which needs replacing now. I believe this results from a faulty manufacturing batch. We will follow up with Volvo, but we got no satisfaction from them when we tried to replace the last riser under warranty.)

Has anyone got any further suggestions on what the problem may be please and some solutions.

 

[shetland]

Try the motor boat forum for a better response.

 

[nigelstgeorge]

Try the motor boat forum for a better response.

Will do as well although the engine is fitted to a Halberg Rassy 53 (yacht)

 

[Tranona]

Classic symptom of the prop being too "big". You are overloading the engine so it is overfuelling which produces the black smoke (unburned fuel). I assume from your description you have a variable pitch prop and it seems that both pitches are set too coarsely.

Haven't checked the specs for maximum rated revs, but would guess it would be over 3000. The prop should be pitched to achieve these revs in normal pitch and your overdrive reduce the revs by probably 4-500 when cruising. This will not overload the engine as the prop will still be able to absorb the power, which it can't do at the moment.

Suggest you ask the prop manufacturer for their recommended settings, explaining what is currently happening.

 

[TQA]

Have you had a look at the prop, it may be a flower pot.

That will give black smoke and usually reduced speed which is what gets noticed.

 

[nigelstgeorge]

Have you had a look at the prop, it may be a flower pot.

That will give black smoke and usually reduced speed which is what gets noticed.

Boat has been in and out of the water and no obstructions on the prop.

 

[nigelstgeorge]

Will do although I am 99.9% sure this has been checked

 

[david_bagshaw]

From our engine tests in the marina tied up against the pontoon


Testing tied up would give completely false results, as there would be a completely different load on the prop

 

[TQA]

OK then you need to get a boost pressure gauge and see what the boost pressure is.

Look to see if the boost pressure control valve is working.

 

[Tim D]

Full revs and engine starts to die back, thas a good clue ... load testing tied up isnt ideal, too much load, why dont you untie it and try it ??

If your getting black smoke under load and its losing power I suggest checking the air filter for a start, even though its had a full service the problem maybe filter related, was this problem there before the service ?? And as an after thought as this is a common problem, carefully check the filter box seal that sandwich's between the filter and the turbo intake, all too often I have seen these not fitted correctly, its possible the seal is preventing the turbo shaft from spinning up.

Also as previously suggested check the boost pressure, IIRC these are not fitted with a waste gate, I can find out the boost pressure but will have to be later on. Not recommended really but you could if very carefull remove the air filter assembly and run the engine, look into the turbo and check for rotation, BUT DONT DO THE OBVIOUS AND STICK YOUR FINGERS IN THERE WHILST THE ENGINE IS RUNNING. Use a mirror to look into it and also keep your hair away from the inlet.

Also check the after cooler ... make sure thats not contaminated with oil sludge. Check for any blocked or damaged hoses being fed or feeding the induction side, make sure there are no splits etc as this will prevent boost pressure.

If you do muck about with the air filter assembly be sure to make sure the small plastic breather pipe is correctly fitted into the filter and to the rocker cover, if the rocker cover end becomes blocked as sometimes happens, mainly cos someone has walked across the engine and stepped on the pipe, you will pump your oil out into the bilge next time the engine runs.