Volvo Penta Diesels Black Soot

[johnmbath]

I recently purchased a 2002 Carver 570 Voyager with Volvo Penta Diesels TAMD74EDC 480 HP each

During the initial Sea Trial, there was Black Soot covering the back of boat, swim step and cockpit area.
We assumed it was due to the engine surveyor pushing the engines to 2600 rpm's.

Recently, we made a 4 hour trip to channel islands, cruising at 1800 rpm's and found the Black Soot was again covering the back of boat.

Any suggestions what would be the cause?

John Bath

[waybomb]

Black soot means unburned fuel
Is the bottom of the boat clean?
What is the wot rpm spec and what is your actual wot?
How old is the fuel?

[johnmbath]

Thanks Waybomb
Bottom paint is new this June 2025.
wot rpm specis 2600 rpm, actual is 2500 rpm
600 gallons of new fuel added August 2025 to 100 gallons existing.

John

[waybomb]

Any idea why you can't get 2600?
Injectors?

[Viper]

Injectors, air filter, turbo, wastegate....

[ck36]

I have a 450 Voyager with TAMD74A engines and have just spent the last 4 months dealing with this problem - and finally solving it (for my situation). The black soot is so difficult to remove from the fiberglass and it starts getting into everything, getting transferred from hands and clothing to interior areas of the boat. It became my number one issue to resolve after purchasing the boat. The first advice I got from most people was "dirty fuel" and since that was easy to resolve I tackled that first without any further troubleshooting. I added a cetane booster (Biobor MD) and biocide (Biobor JF) burned down the fuel nearly all the way, then cleaned the Rocors and fitted new fuel filters, opened and inspected the tanks and then refilled with fresh fuel. No impact on the soot. Since my injectors had been rebuilt a couple years earlier I started leaning towards insufficient air supply. The 450 doesn't have a turbo boost gauge but the EDC does capture it, so I ordered a YDES interface for each engine from Yachtdevices and a YDEG wifi interface so I could read the info on my laptop. I ran NMEA cable from each engine up to the pilothouse and flybridge as I wanted this anyway for future electronics. Once I installed these I could now see boost and fuel consumption on my laptop. I took the boat out and made several runs through the rpm range at 100 rpm intervals and recorded rpm, speed, boost, and fuel consumption. I found that boost was lowest in the range where the boat smoked worst - between 1300 and 1900 RPM. I also noticed that the stbd engine lagged the port in boost and had higher fuel consumption. Above 2000 RPM the smoking mostly stopped and at 2500 RPM the boost and fuel consumption on both engines equalized. At this point I suspected the waste gates on the turbos since my theory was that if they weren't seating properly it would result in reduced air until I reached the point where they were supposed to open anyway. I tried to remove the wastegate but it was impossible to get the allen socket head bolts off so I ended up pulling the turbo off (no easy task since two of the bolts had to be cut and they are a b**ch to get too. I brought the turbo to a local turbo shop and was told that it wasn't worth rebuilding (shaft play, bad wastegate) so I ordered a replacement Borg Warner turbo. The turbo I removed was a rebuilt Borg Warner installed in 2015 and that was the most economical choice since I wasn't going to go with a Chinese knock off. I installed the new turbo and took her out for a run this past week and no more black smoke! Boost at 1750 RPM increased from 22.5 to 28 PSI and fuel consumption dropped from 10.8 to 9.1gph. I have now ordered a new turbo for the port engine and am trying to get the old one off now - more frozen nuts. I'm still seeing some greyish smoke from the port engine and port boost is now less than the stbd so best to replace that too.
Some notes: as part of my troubleshooting I pulled the injectors and had them pop tested at a great local shop (Seattle Injectors) - all were good and there was no charge. I also had a Volvo tech from Pacific Power Group help me with the install and also checked fuel pump timing (only 1 deg off). After removing the turbo you can look into the air side of the CAC and I noticed about 1-2mm of soot buildup but when I recorded temps they seemed ok and it's costly to pull the CAC so I'm not going to do anything there for now. I have an inexpensive boroscope that proved very handy for looking into coolers and cylinders. Great tool to have for troubleshooting. I also had a diver cleaning my neighbor's hull do a quick check of my hull to make sure it wasn't excessively fouled. It wasn't, but it is fouled enough that I can't get past 2500 RPM.
Go through your troubleshooting methodically and I'd highly recommend getting the Yachtdevice gateways so you can a better idea of what's going on with your engines.