Micro soot bubble

Oct 29, 2005
2,355
Hunter Marine 326 303 Singapore
My 14yr old 1650hrs 2gm20f runs beautifully. Sounds pretty smooth. There's no black smoke but only slight white/greyish smoke. New exhaust and mixing elbows.
Question is on long passage I'm seeing greyish bubbles that breaks to soot on water. Very little but noticeable. Should I be concern apart from slight carbon black staining on transom?
 
Jan 4, 2006
6,444
Hunter 310 West Vancouver, B.C.
I'm pretty sure we've got the same setup with the below water discharge. Can't say I've seen anything like small greyish bubbles breaking to soot on the water. I know I've got a problem with my elbow being pretty badly coked up after 4-5 years but I have never seen carbon emissions while running or when idling at the dock after returning . Also, very little carbon staining on the transom.

Just out of curiosity, what condition and age (hours) was your last elbow when you removed it ?
 
Nov 6, 2006
9,885
Hunter 34 Mandeville Louisiana
sounds like a very tiny bit of unburned fuel; I am assuming that this is something new?.. the prime suspects would be dirty bottom and prop.. then from there would be prop pitch very slightly high (would only apply if it had been doing that all along) and then there might be dirty injectors.. or a bad batch of diesel (not as precisely refined) straight from the pump.. Check for a fouled air cleaner as well.. Good luck..
 
Oct 29, 2005
2,355
Hunter Marine 326 303 Singapore
Ralph, my last elbow was pretty old but was decoked annually. Existing new elbow set is only 6 months.
Kloudie, hull and prop very clean. Diesel fresh. Injector haven't been looked at for years. Prop pitch....max I could get is 3350 rpm.
Ok will check out injector. Thanks.
 
Jan 4, 2006
6,444
Hunter 310 West Vancouver, B.C.
my last elbow was pretty old but was decoked annually.
Ken, how did you manage to de-coke your old elbow ? I've used everything from muriatic acid to TNT and the point where the carbon ends and the cast begins is still difficult to determine. Just no luck in scraping it out ! ! !!
 
Oct 29, 2005
2,355
Hunter Marine 326 303 Singapore
Chisel and hammer and lots of pounding
Chisel with a bend tip is effective.
 
Aug 3, 2010
150
Hunter 326 Charleston SC
Ken
Did you go with the stainless exhaust and mixing elbow on E-bay, if so how are you liking it. How many threads did you get on either side of the nipple. Ordered one myself and it's on the way.
Walter
 
Jan 4, 2006
6,444
Hunter 310 West Vancouver, B.C.
Did you go with the stainless exhaust and mixing elbow on E-bay, if so how are you liking it.
I would be most interested in hearing how either of you make out with the SS elbow. I'm considering ordering one simply for the fact that it's about 1/2 the price of a cast iron one here.
 
Oct 29, 2005
2,355
Hunter Marine 326 303 Singapore
Ken
Did you go with the stainless exhaust and mixing elbow on E-bay, if so how are you liking it. How many threads did you get on either side of the nipple. Ordered one myself and it's on the way.
Walter
Yes i did fit the SS U Mixing Elbow. It comes with SS Joint. Thread in as normally with cast iron ones. The exhaust elbow (4 bolts to engine) is stock Yanmar cast iron ones. I haven't open it up to see condition. Perhaps will do so next few months on anniversary of install.
 
Oct 29, 2005
2,355
Hunter Marine 326 303 Singapore
Thanks Ken, I'll be watching for your observations. Maybe the SS will repel the carbon particles (and maybe pigs will fly as well :eek:).
Hundreds years ago no one ever thought man could fly. So I guess its matter of time pigs could do it....why heck the cow did jump over the moon didn't it? :D ;)
 
Aug 1, 2011
3,972
Catalina 270 255 Wabamun. Welcome to the marina
@Kermit should be invited to see this. I hear there's a number of individuals looking to escape the place.
 
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Aug 27, 2015
58
Cal 2-46 Whitianga. New Zealand
Possibly insufficient air getting into the engine. Try removing the air cleaner temporarily and see if this changes things.
I came across one friend's boat recently, dark grey smoke, and found he had negative air pressure in his engine room. Make more air available and problem solved.
Another case, the air cleaner was clogged up, had not been cleaned or changed.
Just a thought.
Pete
 
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
Can't comment on the gray smoke except might be new parts smoking as they get hot enough to burn off any oil coating on them.
As for de-coking an elbow, make a fire in the fire pit and throw the elbow in the coals. When it gets red hot pull it out and dunk it in a bucket of water, repeat as needed. Finish up with getting it red hot again and letting it cool slowly.
 
Oct 29, 2005
2,355
Hunter Marine 326 303 Singapore
I've cleaned up the soot stain at transom. Removed the filter. I'll be motor-sailing next 3 days back to home berth. Will let you know if I'm still getting soot stain.
 
Oct 29, 2005
2,355
Hunter Marine 326 303 Singapore
After removing filter I'm still getting some soot on water. Then I added some STP Diesel Oil Treatment silicone oil. It's helps some but still see some but lesser soot.