View Full Version : Smoking AD41B

02-28-2009, 03:56 AM
"Dear All, new to this forum and wondered if anyone could help? have a pair of AD41B which are driving me nuts! they run fine but produce black smoke when reach 2,500rpm - 3,000rpm just as the turbos kick in, after 3,000 it fine and up to 2,500 it's fine but boy do they smoke just before the turbos kick in, is this normal or can I do something? thanks for your help"

02-28-2009, 09:56 PM
clean the flame arrestors first

02-28-2009, 10:11 PM
Loved Your answer - it's a diesel!!!
To the problem.
Might be several possibilities.
Have You tried running without air filter(s) and open hatches to engine room?
Doe the engines reach max RPM of 3800?
When did You last have Your injectors checked?

03-01-2009, 02:57 AM
Yes we removed air filters and left hatches up, slight improvement, afterwards I fitted two air blowers into the engine space to give the turbos clean fresh air
Yes they reach 3800rpm and checked the dual props were ok, they are
Replaced injectors in both engines and had the intercoolers cleaned?
Had a number of so called engineers look at the problem, all said the same fuel/air is the root cause but none could fix this problem"

03-01-2009, 11:14 AM
"I would suspect that turbo bearing are a little rough, not comming up to speed as soon as they should.

03-01-2009, 11:28 AM
When the intercoolers were taken out to be cleaned, both turbos were removed stripped down cleaned and re-placed by Volvo engineers but still this black smoke as the turbos kick in? you can hear as the engines come up to speed approx 2500rpm look aft and see the black smoke then they seem to over come the load and the smoke goes 3000 rpm? crazy! it drives you nuts because the the aft part of the boat is dirty after use, any more advice or ideas would be great, thanks Roger"

03-01-2009, 09:41 PM
"The only way to reduce this problem seems to be to re-adjust the smoke limiter on the injection-pumps. This need to be done by a Bosch service center with possibilities to run in a test bench.
Your pumps are probably set for 'old' quality of diesel, unfortunately diesel is not what it was when those engines were produced. The downside of adjusting might be that You loose some power during acc and planning.
What has to be done is to take off the top and 'turn' the plunger '29'. The lower part of the plunger is an eccentric cone. By turning, it allows more or less fuel to be injected depending on turbo pressure.

03-02-2009, 03:51 AM
Once again, thank you for your advise, we did take the fuel pumps ashore and were tested and checked the smoke limiter for wear and tear, the pumps were fine and still lock on the settings done by Bosch, you may be right that some ajustment is still required as we may be over fuelling before the turbos kick in, will contact Bosch for the next steps, cheers George"

03-02-2009, 06:24 AM
"The 'secret' is setting of the spring load (30) and the rotation of the shaft (29). It takes an experience operator of the test bench to get rid of Your 'problem', but no big deal. Just have him to reduce the injected amount on the problematic RPM's with correct (turbo)pressure.
It might help him a lot if You hook up a meter and measure Your actual turbo pressure in the affected RPM range, interval of 50 - 100.
Before removing the pumps, double check the timing.
However be careful not let it run too lean!"

04-04-2009, 05:46 PM
"I had the same problem 3 months after I bought used boat with the same engine. Black smoke, later not able to plan under load (but it reached 3900 rpm at rest), solution was - new turbo.Never had any problems since (its been 6 years since and 1200hours)."

04-22-2009, 06:58 PM
I am a new member and I also have the same problem, black smoke when I am on 2500rpm .
I have changed to new injectors, turbos , and airfilters but still the same problem. Engine runs well when am doing 2000rpm but as soon as rpm is increased black smoke shoots out."

10-11-2009, 02:49 PM
As a marine engineer owner of AQAD 40b engines I went through most of the same diagnostics given to try sorting out black smoking when getting the boat onto the plane.

Turns out the solution was not an engineering one. You must get rid of some of the excess weight from the boat and take the old antifouling back to the gelcoat and apply new smooth coating.

Engine is now running fine and gets onto the plane smokeless.

In my experience all boats grow in weight and this soon taakes the boat out of spec for the engines - add a dirty bottom and the engine is overloaded trying to get onto the plane.