Black soot

[kjg1951]

I just came back from a 4.5 hour cruise,upon arrival i had a hugh amount of black soot covering the entire back transom. I have a 1994 28T Volvo 225hp ... what is causing the massive amt of black soot . I was running at 2500rpm at 14 + knots. Any thoughts any additives i should be in ??? thank you for your help and suggestions....

[Tree]

What model Volvo is it? Is it the KAD41 range of engines?

[kjg1951]

kamd 42b

[Tree]

Is it just a soot residue on the stern of the boat? These engines need to be run quite hard, Volvo state 200 rpm below WOT although we always ran out AD41p at around 3300/3400 rpm trouble free for 1200 hours and not the stated 3700 rpm Volvo suggest.

2500 rpm is near the point where the supercharger cuts out on these engines and the turbo takes over. At a guess, if its just a bit of soot on the transom, the engine hasn't been run hard enough, this isn't good for the aftercooler as they will eventually soot up and need cleaning.

If however, you are getting clouds of black smoke then it is clearly something else. Normally, these are bomb proof engines and last for many, many hours of use.

[kathylsails]

I don't know about your engine, but I do know that when we have found a lot of soot on previous boats' transoms, we also find lots of barnacles on the prop. The problem has gone away as soon as the barnacles are removed. I hope it's just that simple for your boat and not something more serious.

[DougSea]

I'm also assuming that's a "conventional" engine with mechanical injectors. A friend with a different engine (Caterpillar 3116) had the injection timing adjusted and found that he gets a lot less smoke and soot. Over time the injection system "retarded" itself and was no longer firing at the right time, causing soot and reduced power. Might be worth checking out.

[kjg1951]

Here is a pic of the transom and swim platform ... i dont have a large amount of black smoke visible when under way ... I am going to try to add Valvtect Diesel Guard Heavy Duty/Marine additive as per my Volvo mechanic. He tought the injectors needed a cleaning....

[Tree]

If you do have the injectors reset, make sure the company doing them are aware the nozzles are bronze - injectors are normally done at 1000 hours or so.