starboard engine smokey (grey) over 1400

[Genevatexan]

My starboard engine is a little more smokey this year than last having owned the boat 2 years. The port engine (DD 6-71s) was rebuilt in the 80s and the starboard one is a little weaker. 25 lbs oil pressure at idle, good compression, no obvious issues, just smokey with the throttle up.

A friend with 12-71s suggested pulling the intercooler and checking air and water sides for blockage. I plan on doing that next weekend, and have the furniture out and the carpet up and the engine exposed. But before I do, I could use some guidance:
1) The heat exchangers were major league plugged when I got this boat. The owner did not use it for long periods of time and the exchanger channels plugged up with crystalized moss, minerals and crud. the starboard was 90% and the port was about 70%. I cleaned and resinstalled them on advice from this forum and they ran a steady 170 at all speads now. So my first question, if the heat exchangers had a big proplem, does it follow that the intercooler will also be plugged? 2) does water blockage on the intercooler lead to overfueling somehow? I would think this would be more likely on the air side-- not enough air, too much fuel...3) I checked the turbos behind the walker airseps and there is some oil discoloring on the blades but not dramatic. If the turbo blades are pretty good, what would lead to plugging on the air side? (If its not aspirating oil....)

Everything is sealed and working and replacement seals are high, so I dont want to pull them down needlessly. I am just trying to understand if an engine looks smokey, not black smoke, still has good compression and power, could the grey smoke be caused by blockages, either air or water in the intercooler?
Thanks, Kent

 

[MikeP]

I don't see how an intercooler/HE issue could cause grey smoke. Are you sure it's smoke and not steam?

I have pulled my HE/intercoolers several times to clean them. THe last time, in summer of '10 I pulled/cleaned them and found that while the HE had deposits and needed cleaning, the intercoolers were essentially clean. I don't know why this should be the case but it clearly was.

Obviously the raw water in the HE ends up being much warmer than it is in the intercooler and perhaps that increased the reaction that causes the deposits. I don't know but it's an obvious difference - at least on both of our 8V71TIs.

 

[REBrueckner]

I agree with Mike's post above....

First thing I'd check: ....Have you changed ALL fuel filters recently?? Oddly, a fuel RESTRICTION can cause smoke.... but when dirty filters and or fuel happened to me, exhaust smoke was black at 1500 and up....seemed clear at moderate 1,000 RPM.....changing filters corrected the "problem"....

"A friend with 12-71s suggested pulling the intercooler and checking air and water sides for blockage."

Good idea...can't hurt...but only if I was positive my fuel filters were perfect...


1) So my first question, if the heat exchangers had a big proplem, does it follow that the intercooler will also be plugged?

Unlikely maybe a big air blockage.......If they are disassembled, good idea to pressure test them for any water leak...doesn't seem a water blockage would cause smoke especially since the engine temperature is ok.


2) does water blockage on the intercooler lead to overfueling somehow? I would think this would be more likely on the air side-- not enough air, too much fuel...

unlikely..but water intrusion MIGHT cause some exhaust steam....but warmer air would be a bit less efficient than cooler (water cooled air)....

3) If the turbo blades are pretty good, what would lead to plugging on the air side? (If its not aspirating oil....)

a partially closed air shutdown??? or a fouled (dirty) intake air filter....or a collapsed air hose...are all the air sep hoses in place...none loose or fallen off...??


How do you know compression is good?? Problem might be a slightly faulty (worn) injector and/or dirty injector.

Good luck......

 

[saltshaker]

I would start with the fuel filters, both primary and secondary. Also make sure you have a clean bottom and running gear. My first indication of a fouled bottom or fuel filters was always a bit of white-grayish smoke. Also make sure the smoke isn't water or coolant. Check your coolant levels and see if the smoke has any odor.

 

[Wired]

I had gray smoke from one of my 8-92s this season. Removed and cleaned the intercooler, replaced the Airsep filter. Checked and cleaned the small bit of black oily stuff from the turbo blades, replaced (needlessly) the fuel filters. Tried canceling out the injectors one at a time to see if that would identify the culprit.
Ended up finding out I had 2-3 injectors overfueling. Had a set of eight onboard so I went ahead and replaced them all.
No more smoke.
So much improvement that I'm now becoming dissatisfied with the other engine which up to now looked clean!

 

[Genevatexan]

Great feedback. Coolant level not dropping, no odor, exhaust is not steam, we had 70 degree days this weekend so no confusing with cold outside air, this is blue-ish, no white at all. Had engines tested at purchase by Stewart Stevenson who noted compression good, although no readings. Comment was based on manually barring over the engine. Injector seems likely culprit, though fuel filters surely need replacing. Will do those first. What process did you use to isolate each injector? no oil in exhaust that I can detect, oil levels consistent. See attached pics of heat exchanger project that I completed on advice from this forum last year. Very bad, and had to clean immediately. Complete bottom job last year, with consistent use since. I also use valvetec diesel fuel and Cetane booster for every 100 gallons....

 

[MikeP]

WOW! Can't imagine that engine could run at much more than fast idle -if that - for more than a few minutes.

 

[Genevatexan]

About 1,000 rpm at the sea trial was all she would hold. After that, overheating. Here's the after view. (this is why I am asking about the intercoolers... this was not an average situation...)

 

[REBrueckner]

Given how that heat exchanger looks, never seen one so "cruddy" yes, I'd check the intercoolers just on general principles and for peace of mind....

I had an Onan HE which I took apart and that was maybe 35% clogged....afterwards the genny ran ten to 15 degrees cooler.....the cast iron end cap "rust" had "grown" into the copper based cooling tubes...especially on the suction side...but also the discharge side...

 

[67hat34c]

Cant hurt to go through everthing, very likely you will find many things that need repair-replacement.

I helped another member here clean his HE and it looked very much like yours.

 

[Genevatexan]

Pulled down the intercooler this weekend and found the air and water sides clear. Looking down the tubes of the water side there was literally no deposits or blockage. The tubes diretly in front of the the in and out pipes were perfectly clear and bore no resemblance to the mess we found in the heat exchangers. The air side had a very light amount of discoloration on the cooling blades. HOWEVER, a number of fins are missing off the bottom cross tube, and it even looks almost like there may have been one more tube at the bottom... can someone look at this and tell me how serious the issue is? It does not seem to affect engine performance....look at the bottom row, right hand side. As the intercooler is installed this is the angled up side of the two bottom corners...

 

[REBrueckner]

If it pressure tests ok, I'd not worry about some missing fins....If $1,200 (just a guess estimate) means nothing to you, then go for a new one...