3 hour tour

Oct 22, 2014
20,989
CAL 35 Cruiser #21 moored EVERETT WA
Only 3 sources I can think of are:
  1. Carbon soot from diesel. If oily possible blow back from breather, or exhaust
  2. Belt dist from alternator belt. This could be every where not just in bilge
  3. Black mold. But looks to much in a defined spot so not likely.

 

Apex

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Jun 19, 2013
1,197
C&C 30 Elk Rapids
is it oily/slick? Could it be transmission oil, not engine oil?
 
Jan 11, 2014
11,321
Sabre 362 113 Fair Haven, NY
I assume you checked the fluids so you would know if it was oil or transmission fluid.

Another place to check is the stuffing box or shaft seal, the hose could be deteriorating. That would account for the fluid, seawater, and the black particulate.
 
Sep 5, 2019
39
Hunter 386 Rock Hall
How about the foam air cleaner. I’ve had one deteriorate and throw black dust everywhere. Very similar to belt dust.
 

RoyS

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Jun 3, 2012
1,739
Hunter 33 Steamboat Wharf, Hull, MA
Check Engine Exhaust Mixing Elbow. Could be a rust hole dripping cooling water with carbon soot into bilge.
 
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Jan 11, 2014
11,321
Sabre 362 113 Fair Haven, NY
Check Engine Exhaust Mixing Elbow. Could be a rust hole dripping cooling water with carbon soot into bilge.
Yep, that was one of my later thoughts this morning. Yanmars have a reputation for mixing elbow rot. Also check all of the exhaust hoses and the muffler.

Edit: And if the mixing elbow is the culprit, don't use another Yanmar OEM part. Go to HDI Marine and get a nice stainless steel one.

 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
You can do some simple tests that might give you a clue by putting some black residue in...

1) Vinegar
2) Hydrogen Peroxide
3) Drano [ a few grains in solution ] or Liquid Plumber

If no response to the above,

Heat some very hot in Aluminum foil on the out door grill.
____
One or more reactions will tell you the source.

Jim...

PS: You have problem, adventuring out without finding the source, is not a good idea
 
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Feb 14, 2014
7,399
Hunter 430 Waveland, MS
He recommended us cleaning it with some Mean Green
I did a bit of quick research on that.
Not on my boat, ever.

Paper towels seem best method of cleaning, after you eliminate the source.
Jim...

PS: Diesel Mechanics clean stuff with a lot of things not used around people or parts found on boats.
 
Jul 27, 2011
4,988
Bavaria 38E Alamitos Bay
It might have been better to have saved a sample of the stuff and have it closely examined—chemically or microscopically. Then, you might have deduced what it is; and next, whence it came, etc. Nevertheless, black residues suggest carbon content from burning or other type of degradation, which could come from nearly anything these days. Another idea is to contact the previous owner, through the broker if necessary, to inquire if it has been seen before now.

Also, re:mixing elbow. My Yanmar came with a SS elbow still fine after 20 yr. So, there is probably a Yanmar part in stainless.
 
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May 7, 2012
1,338
Hunter e33 Maple Bay, BC
It might have been better to have saved a sample of the stuff and have it closely examined—chemically or microscopically. Then, you might have deduced what it is; and next, whence it came, etc.
:plus:

Could it possibly have come from an ice box/refrigerator via the drain? Or something liquid stored in or around the bilge? Again without the evidence it will be more difficult to solve.
 
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Oct 26, 2010
1,882
Hunter 40.5 Beaufort, SC
[QUOTE="Kings Gambit, post: 1612766, member: 106217"

Also, re:mixing elbow. My Yanmar came with a SS elbow still fine after 20 yr. So, there is probably a Yanmar part in stainless.
[/QUOTE]
I have a 1994 (constructed in 1993) Yanmar 4JH2E that has a bronze exhaust elbow. I called HDI Marine a few years ago to inquire about a SS mixing elbow in case I wanted to replace it. They told me they (at that time) did not have a SS mixing elbow for that particular model Yanmar. They told me to check to see if it is bronze by making a scratch in the surface and if it is "bronze" color, that is what it is and there is no need to replace it. The bronze should last as well as the stainless. besides, I have a habit of running at full throttle for a few minutes after motoring to blow out any carbon that might accumulate. I scratchted mine and sure enough, it is non-magnetic and has that bronze look. I don't know if it came this way on all 4JH2E's or not. Anybody else have that model with a bronze mixing elbow. I don't think the PO's modified it, but who knows for sure?
 
Apr 11, 2010
946
Hunter 38 Whitehall MI
:plus:

Could it possibly have come from an ice box/refrigerator via the drain? Or something liquid stored in or around the bilge? Again without the evidence it will be more difficult to solve.
not on this boat, the refrigerator and separate freezer are more like an apartment style refrigerator and they do not have drains.
 
Oct 2, 2008
3,807
Pearson/ 530 Strafford, NH
If it was fresh water rather than salty, that might be from a shower, sink, or mast if keel stepped. I’ve spent a lot of time cleaning my sumps and bilges and any waste hoses to reduce the breading ground for mildew etc. There might be a chance that the sound barrier around the engine has foam slowly crumbling. We had that too. I replaced what I could do and the rest I covered with heavy tape.

Try to duplicate or press on the sound board material.