YIKES Belching Oil!!!

[go boater]

So a little mishap on Memorial Day weekend caused me a 3hr cleanup of the engine room.

To lay the groundwork, we've got 1987 vintage JT 6-71's @485 hp that blew a hole in the rubber fuel cooler hose (sea water). Before we realized what had gone wrong, we had just run 2 hrs @ 1950 with no problems, fueled up 400+ gals and tried running her back up on plane. She started belching black smoke (unburnt fuel) and turbo wouldn't kick in on this one motor. I noted that the turbo had stuck on that engine once before after sitting so we tried running her up without a load to listen for turbo or to hopefully unstick it... nothing. Tried running her with a load 2-3 more times onto plane and she wouldn't turn up.

We limp to port for the night, find that a 1" hose blew and got a replacement installed ASAP. Next day we test at dock (turbo working without load) and upon departure we easily get up on plane but blowing some black smoke on same motor for 90 seconds or so until it cleared up. Once clear, all seems well, we run for about 2 hours before stopping for the night. Just before bed I do my engine room systems check... WHOA! Bilge full of oil - probably 1-2 gals in total from the motor we just had problem with the day before. OIL is covering EVERYTHING and finding root of cause takes some considerable cleaning and guess-work.

Judging by the concentration and foam silencer pad, the only thing I figure could have done it is that the air silencer or oil breather barfed up a bunch of oil after we did the hose repair. Odds are this may have happened as we got onto plane and saw smoke for 90 seconds as the turbo began working under load again. Any ideas what would cause this?

After topping off the oil and cleaning the bilge, we inspected at WOT, and other RPMs - no problems sighted. We then put 7 more hours run time on her between 1000 rpm and 2100. Aside from residual oil in the engine room from the night before, all seems to be completely okay.

I'm the first to admit that I'm a total novice when it comes to diesel repairs and diagnosis (at best). Any thoughts as to what caused this or why it happened???

Thanks in advance

[seapower]

PM sent, Frank

[go boater]

PM sent, Frank

Thanks Frank!!! I think your theory is correct. I sent you a PM back - you're welcome to post for the benefit of all readers. I hope that there wasnt any long-term harm done to the motors but they do run great after the buildup and they had plenty of hours after the fact for them to prove me wrong.

[54bullwinkle]

Hey cap , what was the problem.

[go boater]

Hey cap , what was the problem.

I think Frank / Sea Power can do the best job summarizing it in the PM he sent me. While I can't suggest that the facts are the same seing as how I don't have AirSeps, he knows his stuff for sure.


"Didn't know whether to post this up or not? Anyhow, do you have Air Sep's on this engine? If so I'd have to guess (only thing I can do without being there), your turbo was probably slowing down from the salt water injestion and didn't have the vaccum (from lack of RPM's) to pull the oil rich base compression through the oil seperation wick. The seperated oil drain's back down into the base through the drain hose and check valve arrangement.
Some thing else that may have happened (this comes from you saying that the turbo was stuck before). Your turbo has 2 turbines (one intake side, one exhaust side) with a common shaft. On the shaft there are oil control ring's, if the shaft or rings are worn, as the engine was running without the turbo turning, oil may have pushed past the ring's. Boost pressure on the inlet side help's keep the oil back. That's why you see alot of oil accumulation at the air cleaner on engine's that are run at low rpm's. There isn't enough boost pressure and the oil pressure wins. Again don't know for sure, but it sound's like the turbo was the only thing taken out of the mix. Frank, SeaPower"

[seapower]

I mentioned to him after finding out he didn't have AirSep's (which I highly recommend, for marine installation's), that he may have had an excessive amount of exhaust back pressure. By the turbo being slow (or not turning at all) because it was sticking from saltwalt intrusion, the exhaust side turbine would have actually caused an exhaust restiction (excessive back pressure). This inturn could have caused excessive base compression that may have resulted in the puking of oil. Can't say for sure I wasn't there, just a thought. Frank,SeaPower

[go boater]

Frank is the man - thank you very much for the feedback. If anyone else has additional insight / confirmation of this theory that they don't mind sharing, please share away!