Sudden Onset Black Smoke - Yanmar 4JH-DTE

[Ex-Calif]

I'm with badsanta regarding the prop. If you can't get full RPM and this happened on next start, I would suspect the prop was indexed a tooth off or more on reassembly.

We have a max prop duo. It would also foul from one month to another if given a chance but we don't leave the boat idle that long. What happens for us is a gradual reduction of top end and when it reaches time for a cleanup we start to get black smoke and a max RPM of about 1,800-2,000.

Depending on the model you have there are gears on the blade roots that index into the pinion gears (2 each) then the pinion gears index into the drive gear. That's 3 locations your diver could have gotten the indexing off.

I have been told there is a technique where the zinc can be split by a saw so the prop doesn't have to be removed. We never saw need for that as our prop is off at least once every 15-18 months at haulout time.

Our zincs cost like 8 bucks so we put a new one on every time while also lubing the gears. Preventitive maintenance on the underwater stuff pays itself back in spades.

[Microship]

Good news, folks! I sent a diver down, and he reported massive encrustation of bio-fouling... apparently this is the worst year in their memory. Running gear had lots of mushy stuff and barnacles, and the whole boat was covered.

I had the team go polish her up, and I am very happy to report that the black smoke is gone. Even 3200 RPM passed without incident...

Thanks for all the advice and commentary - this has been educational! I never would have guessed the effect could be this dramatic.

Cheers,
Steve

[MarkJ]

Originally Posted by Microship

massive encrustation of bio-fouling...

Damn those Greenies!

Well done on getting the solution, Steve

[roberttigar]

A clogged air screen could very well be your problem causing black smoke. Diesels need alot of air to complete combustion. A restriction of the air flow would mean unburned fuel.
Proper leaning of the air screen should be done by soaking it in kerosene (a lite wt diesel fuel) or the diesel you burn. Thqat will remove the dust, dirt etc. Bob

[sokari]

Black smoke is caused by incomplete combustion,In this case as others have said a fouled prop or something you can check is the stern gland has not tightened up .
Any how everyone has you on the right track if it is not happening in nutral then it is in the drive train.
You can turn the shaft by hand and see how stiff it is.
One other thing would be to check the heat of the stern gland while running(be careful doing this).
All the best John

[Tellie]

I'm amazed that the first thing people don't do is dive the prop on a regular basis. Clean air, clean fuel and a clean prop.

[Microship]

Originally Posted by Tellie

I'm amazed that the first thing people don't do is dive the prop on a regular basis. Clean air, clean fuel and a clean prop.

Yep, this is how we learn. The take-away from all this is that I must have a way to get down there... wetsuit, MFS, and practice. A quick eyeball on the prop would have answered a lot of questions, even though I would have still needed help getting the bottom cleaned.

Thanks again for the advice, folks!
Steve

[Tellie]

Originally Posted by Microship

Yep, this is how we learn. The take-away from all this is that I must have a way to get down there... wetsuit, MFS, and practice. A quick eyeball on the prop would have answered a lot of questions, even though I would have still needed help getting the bottom cleaned.

Thanks again for the advice, folks!
Steve

Hey I'm a Florida Boy, for all I know you might be living in those fridged waters up north where the water temp. gets below 80 degrees. I hate cold water outside of a glass!

[Microship]

*grin* indeed. It's 45 degrees at the moment. Even with a borrowed wetsuit, I was gasping, and there was 3 knots of current in the anchorage. Diving under the big dark hulk of the boat was kind of intimidating (which is not to say I don't need to overcome that, but my one opportunity to try it was not successful).

Cheers!
Steve

[Ex-Calif]

Originally Posted by Microship

Yep, this is how we learn. The take-away from all this is that I must have a way to get down there... wetsuit, MFS, and practice. A quick eyeball on the prop would have answered a lot of questions, even though I would have still needed help getting the bottom cleaned.

Thanks again for the advice, folks!
Steve

Depending on where you are you can also snag a rope, fishing net or other debris that ruins your whole day.

A few weeks back we snagged a good chunk of polyprop. No wind and we were turned into drifters.

I had to free dive three times to get it off. In addition to not being that great a free diver, my buoyancy and the current resulted in me bumping the hull a lot. I was a bloody mess - ouch.

[Microship]

Ouch! Just imagining bumping my noggin against a barnacled hull - I didn't even think about that problem.

I'm going to fast track the underwater camera project, even with just a kluge deployment on a boat hook. Peering at it would have eliminated a lot of stress about potential engine problems.

Dive gear too. Need to be able to get at the key bits, as well as dive on the anchor.

Cheers from a bouncy night on the hook off Camano Island...

Steve

[Robertcateran]

A small battery operated hookah makes the job a lot easier

[captain58sailin]

Has anyone ever used one of those shaft spurs, to keep their props free of ropes etc...?

[Microship]

Originally Posted by Robertcateran

A small battery operated hookah makes the job a lot easier

Definitely on the wish-list, that!
Steve

[SkiprJohn]

All right Microship, you don't have one of those remotely operated underwater cameras? Jeeez!

Glad you found the problem without too much expense.

Kind regards,

JohnL