Volvo AD41 Black Smoke Low Revs

[Tim777]

Help! I have a Targa 33 with two AD41A engines. The port engine yesterday was reluctant to rev when going onto the plane and we noticed a pall of black smoke and fuel / oil? deposits in the water. We eventually did plane but the engine did not want to pull to full revs. (3200 was max) Out of gear back on the berth the engine would achieve full revs, air filter is clean, as is crankcase breather and turbo seems to turn ok. Primary fuel filter also seemed ok. Engine oil ok and temperatures ok. I was wondering about the smoke limiter but would welcome some more ideas. Thanks
ps we have had smoke going onto the plane for a little while now but this is the first time we have had a limited performance from the engine.

 

[PRH]

Could be a dirty bum. There seems to be a lot of growth in the last two months, makes them work harder, just a thought though there is obviously some difference between the two engines. Seems the black smoke just before they get on the plane is quite common, they are working hardest then.

Suggest you get Col to look at them.

 

[Nauti Fox]

We had that at the weekend and it turned out to be a broken clip holding the hose between the turbo and intercooler, not saying it's that, but worth a look.

 

[DAKA]

Did you try the filter block test ?

3 mins
Full revs starboard side.
tickover port

then push port fully open
boat should leap onto the plane or at least surge forward before your revs then fall back.

this would indicate a filter blockage and time to change primary at least.

 

[brianrunyard]

OP states it's only the port engine that's affected, dirty bum would affect both engines.

 

[TRH]

Could be your Turbo not kicking in under load.It happened to me.

 

[dalex]

AD41 same problem but both engines.
Make sure the engine is off and cold before trying this!
Unscrewed silver cannister filter from rear of manifold. removed turbo air filter.
Fingers into mouth of turbo. Turn impeller with fingers - should turn very easily and spin with a twist of your fingers. Mine were stiff at first, and I felt a crunch and click then all nice and smooth. I suspect running the engines at low revs caused a build-up of carbon on the exhaust impeller which broke off when turned by hand. Re-fitted turbo filter and manifold filter. Both turbos spool up properly now, and plenty of oomph!
Costs nothing but time, but don't drop your screwdriver down the back of the engine when undoing the turbo air filter jubilee clip. Local installation clearance will dictate the order of filter removal. Good luck!

 

[hlb]

Theres nothing fresh about AD 41's smoking. They do it just for fun.

Change the fuel filters and try again. Look for the obvious and easiest first. This time of year. All the filters should be clean. You did this through the winter, did'nt you. You should also have a reasonable clean bottom. Chech this, then look at the rest.

 

[Tim777]

Thanks for all the replies !

Dalex - I have taken the crankcase breather and air filter off and spun the turbo but need to take the boat out again to see if I achieved anything - didnt feel a "crunch" though. Will compare the spin to the stb engine

Hlb - Yes I think I will change both filters as a matter of elimination - seems v sensible

Unit 18 - will check connections

Will post when solved !

 

[jaws]

You could might want to check the fuel cutoff valves are fully open. I had a fender resting on a fuel cutoff cable on my previous boat and when I reved up it pushed against the cable partially cutting the fuel off. When I slowed down the fender rocked back and the cable relaxed and the valve opened again.

Symptoms where low revs and black smoke.

Took ages to diagnose!!

 

[Nick_H]

Your problems sound similar to those I experienced on my port engine on the last boat. It started and ran OK but wouldn't reach full revs, and there seemed to be a bit more smoke than the stbd engine.

Col traced it to the injectors, which were injecting a squirt of fuel rather than a spray and therefore combustion was incomplete. The symptoms sound similar and its a fairly cheap and easy thing to get checked, so might be worth a look. It would explain the fuel deposits on the water as well if not all the diesel is burning.

 

[Col]

Have the tappets been done recently?
Was the air filter clean? That would cause probs if dirty.
Otherwise..
fuel / fuel filters
injectors
turbo
pump