Smoking engine

[scott]

44 tri cabin has twin 8V53's with 1400 hours. Port engine is smoking a bit at 2200rpm. I checked the oil level and it appears well over the full mark and could have been overfilled at the last oil change. Would this cause the smoking?? Has not done it before. Appreciate the help from anyone.

[Captcoop]

I would look at the fuel system starting with the filters. Water in the system will cause smoke. Good Luck

[Nonchalant1]

What color is the smoke? Different color = different cause.

Doug

[Genesis]

White smoke = either unburned fuel (e.g. blown injector tip, so you're pissing raw fuel and its not burning) OR water (steam) - the latter is discernable because it evaporates within 10-20' of the rear of the boat. The later (small amounts of steam) can be NORMAL on some engines and exhaust systems under certain atmospheric conditions.

Gray/Brown/Black smoke = Too much fuel for the air available. Restricted air intake or exhaust, on turbo engines restricted after or intercooler, or bad turbocharger. Radically incorrect rack calibration or bad injector (SERIOUSLY bad) Easily visible as a "haze" behind you.

Blue smoke = Accompanied by high oil consumption - excessive oil pass-through to the cylinder. Lots of causes on a Detroit for this - one of the more ugly is bad blower seals. If these fail entirely while operating the engine will run away! Do not ignore leaking blower seals! Other "more traditional" causes are bad piston rings (accompanied by high crankcase pressure) and bad valve guides (also usually accompanied by high crankcase pressure, since what goes in will also come out). Finally, in a turbo engine a leaking center housing can cause this - do not ignore this one either, as it too can cause a runaway or a grenaded turbocharger (that tends to do ugly things like start fires in the engine room, eject parts at 100,000 RPM, etc)

[GeorgeC]

I've seen a few post now referring to runaways. How common is it? Are there warning signs and if it happens, what so you do? Recent post talked about stuffing a rag in a runaway generator, but thats not practical on a main engine. Isn't that the sort of thing the emergency stop is for?

[Genesis]

...... is failed blower seals. Second is failed center housing seals on turbo engines.

This is really nasty. The engine will run on its lube oil - until its all gone! The governor does NOTHING. It doesn't run WELL, but it does RUN.

Taking the engine out of gear will likely lead to an immediate overspeed and pieces in places you don't want them.

If you have airdoors, pull them. Not all Detroits have them - in particular, some 6V92 applications do not have them.

If you DON'T have them your only hope is to stuff something in the intake. This is very hazardous on a turbo motor for obvious reasons, and on a non-turbo motor you have to make sure whatever you stuff in there can't be aspirated - if it goes down the pipe and into the blower, you will also get pieces, although often that damage stops with the blower (the blower drive shaft will break in extreme cases)

Shutting off the fuel doesn't help for obvous reasons - the engine is running on lube oil. Also obvious is that it will stop - when the oil runs out! Not good....

The danger is that if you get into an overspeed situation the engine can literally explode and flying conrods along with pieces of piston and crankshaft can punch holes in the boat - or you.

If you have excessive oil consumption (more than a gallon or so in a full day of hard running) find out WHY and fix it. There usually is plenty of warning of something like this in the form of excessive oil consumption for a while before it happens.

Second if you ever DO use the airdoors, inspect the blower oil seals before you restart. Its possible that degraded seals can be pulled in during a high-power shutdown using the airdoors, and if they are, the engine will immediately run away when restarted - since you start out of gear, if this happens to you on a startup you're instantly screwed.

This kind of thing doesn't happen often but if you ever do have it happen in your presernce its not something you'll forget.

[jim rosenthal]

..in theory any engine that runs on oil as fuel and ignites it by compression could run away. In practice, is this confined to DDs or does it happen to other makes as well? Just curious. What else puts a diesel at high risk for a runaway...
Interestingly, my Mercedes diesel (a car) has no provision for cutting off the air except, as you say, stuffing something into the air intake. Whoops.

[Genesis]

... with some regularity.

Turbo engines are the big culprit, in that failed turbo seals can do this - and sometimes do.

Detroits have the blower as another potential oil (fuel) source. That's it.

[Nick]

Karl,

Is there a way to check the turbo seal integrity ie. play in turbo wheel shaft or are there any signs of oil on the intake side of the turbo? I have noticed slight blue smoke when my 671TI engine idles down to about 150F at idle. No smoke is evident at cruise. The oil consumption seems to be about 2 quarts every 20 to 30 hours of combined running, trolling and fishing.

Nick

[divernc]

Friend had this happen to a 4 year old Cummins in a 1997 Bertram 36, when an injector line suffered a hairline fracture that sprayed fuel in the vicinty of the turbo. He was in gear, running on plane and when it started to runaway he pulled it out of gear and a rod threw. Trashed engine, no hull punctures, no warranty, BIG bill.