Transom soot and black smoke

[bobk]

What all can cause these symptoms? We docked in Southport NC some days ago and all was well. When we arrived in St Augustine, we found a lot of soot on the transom and saw black smoke belch from the port engine when I goosed it in reverse for picking up a ball. It happened again last night in New Smyrna Beach.

I'm guessing we lost an injector because it came on suddenly, but what else should I worry about. After coolers were last cleaned 3000 hours ago, but we run 1000-1100 rpm, so easy use. My mechanic is going to look at it next week, but I'd like all ideas.

Bobk

 

[kelpy]

You don't say what engines you have or when they were last tuned up but I assume they are Detroit 92s if they are aftercooled. If they are DDECs, you will get an alarm if you lose an injector.

If it has been more than a year since the last tune up, I would have the injectors pulled and tested/cleaned. Then have the engines tuned - adjust the valves, set the racks (injector heights if DDECs) and confirm high idle RPM.

The after coolers (or inter coolers) will certainly need to be cleaned after 3000 hrs. When they are dirty, they will severely restrict the airflow causing black smoke and contributing to the soot on the transom. This means pulling the blowers to get to the after coolers but it has to be done.

 

[MikeP]

Check the easy stuff first - check that the air filter(s) are clean and that there is no obstruction to air flow…a loose rag in the ER flying around and getting sucked onto the surface of the air filter, collapsed air filter, etc…

Then proceed to the wallet-lightening items.

 

[bobk]

Thanks guys. They are 6V92 425 hp. The problem seems to have come on suddenly. We had run 2200 miles this year before the issue started so I'm assuming a fast occurrence like an injector. The vacuum limiters would have indicated a blocked filter so I'm OK there. Fuel vacuum gages are well in the green.

Morgan French out of Stuart does my DD work there and I have him scheduled for next week. Is there any way to diagnose dirty after coolers? The last tune up was probably 500 hours back. I have a DD mechanic look they over when I get north every year and he didn't make a recommendation to tune them but maybe it is time.

Bobk

 

[Boatsb]

What about engine mounted filters?

My Dad had a similar issue. His mechanic didn't bother with the engine mounted fuel filters. One was almost solid when they pulled it.

 

[Finalee]

A crab pot line around the prop could do it.

 

[jim rosenthal]

Seems like black smoke and transom soot (which are unburned fuel, right?) would result from too much fuel going through the engine and not getting burned to make power.

I had this problem with my Caterpillar 3116s. There is a device on each engine (Derek would know the name of this thing, which I don't) that opens the rack and increases the delivery of fuel as the turbo boost comes up, essentially matching the fuel delivery to the amount of air that is available to burn it up. As the turbo boost increases, so does the fuel amount via the injectors. I don't know how DDs accomplish this, but I would think something has to match fuel metering to manifold pressure (since the engine can't measure the amount of air delivered, directly- it has to infer it from manifold pressure, right?) Perhaps this isn't working correctly?

Too much load could do this as well (crab pot line or someone's old anchor rode) Seems to me that a restriction in the fuel delivery path would just cause less power and a lower rev ceiling, but NOT smoking or transom soot- since diesels are supposed to have excess air for each power stroke, a restriction in fuel available to the engine would just act like the rack wasn't opening all the way.

 

[Boatsb]

Turbo?

 

[johnjen50]

I'm with Scott on this at least initially. A seized turbo, which I just experienced, will cause black smoke behind the boat. Easy check to take off the airsep and stick your hand in there to see if the blade spins easily. Mine didn't, so I'm going to take it off and try to figure out why it happened. Check the easy stuff first.

 

[kelpy]

It very well could be a seized turbo. If it is though, you have even more headaches repairing either your exhaust system to fix the water intrusion problem or the turbo cartridge itself. I don't know of anything else that would cause a turbo to malfunction in a normally running engine.

In any event, the after coolers are overdue for an inspection after 3000 hrs.

 

[Tim Powell]

Turbo?

my dollar is there to. especially if they are dry ones. Stick your finger in the end and see how much play.

 

[saltshaker]

Turbo is a good guess but would it matter at the speeds he's running? I don't think there's much boost at 100rpms which is where I believe he said he is running. An injector that is stuck open or has a poor spray pattern can do it, an air restriction can be the issue among others. Check the easy stuff first and if no luck see what your mechanic comes up with.

 

[bobk]

Thanks everyone. We got back to Port St Lucie late yesterday and I'll be digging into these suggestions.

Jim, my mechanic changed the things you mentioned when I bought the boat 9 years ago. He called them 'levers'. Perhaps one is bad.

Air filters were checked in June and looked fine. My mechanic didn't think it was worth cleaning them. I can't bend enough to reach the out board filters so I have to leave them to the younger guys.

Re a crab pot line, I did experience a slight vibration after the launch at Atlantic Yacht Basin. Will have to look into that. The running gear was primed and painted with hard Pettit which I figured was the cause.

Turbo? Yes, not much soot at slow speed, but it was so bad yesterday when I tried to open it up to 'blow out the carbon' that I had to immediately return to 1000 rpm which cleared the smoke.

I'll get down there this morning and start through the simple things.

Bobk

 

[captddis]

Check the turbo clamps first.

 

[bobk]

Check the turbo clamps first.

I didn't know they could loosen. Isn't there a sealant behind them as well? But I surly will check.

I had a good look at the filters and they are clean. Also thinking about the 'levers' if that is the correct term, wouldn't they cause smoke on acceleration but not after the engines are wound up? If so, I can eliminate them as a possibility.

Bobk

 

[saltshaker]

Turbo? Yes, not much soot at slow speed, but it was so bad yesterday when I tried to open it up to 'blow out the carbon' that I had to immediately return to 1000 rpm which cleared the smoke.

I'll get down there this morning and start through the simple things.

Bobk

Sounds like a turbo issue based on the above.

 

[Fanfare]

Always check the emergency air shutdowns at the blower to be sure one is not tripped. Sometimes they only partially shut and might cause this.

Say Hi to Morgan for me, who has maintained Fanfare for probably close to 40 years.

 

[Summerfun]

I think a lot of these issues mentioned would cause a lot of black smoke. The turbos not spooling on my boat means that it looks like a train behind the boat. And the engine will not get up to speed. Have limited kwnolage but have had the same issue on my boat. One engine I had rebuilt runs clean the other has a light tinge of blackish smoke. This leaves a trace of soot on the transom when I get back to the slip. My mechanic has chalked it up as a intermitaly bad injector. You can here it as it idles. I am having all the injectors replaced before it goes away for the winter. If you have a small amount of soot after a good run I won't think it it a turbo issue or an air door issue.

 

[bobk]

6V92 TAs, no air shutdowns. Yeah, I'm starting to bet on turbo's too.

Bobk

 

[bobk]

Well here is an update: Morgan French looked it over, found the turbos looked good based on dry side inspection and decided to pull all the injectors. He took them to a shop in south Ft Lauderdale that he trusts. The report was some were sticky what ever that means, but not especially carboned up, and so all were replaced with rebuilds. In reassembling, he found one 'push rod' (my term?) was stiff, but not damaged. I'm not sure what he did with it, but the engine started and ran well at the dock after assembly and didn't generate any black smoke when goosed moderately. We'll get a sea trial in next week.

These injectors had 3700 hours on them. Is that a good life time for 6V92TA's? And would you expect more life if I was using a lubricating additive in the fuel?

Bobk