Yanmar 4JH3-DTE needs to quit smoking

[jt11791]

My Hylas 54 is equipped with a Yanmar 4JH3-DTE turbo-diesel which makes an embarrassing amount of smoke on start-up. After it warms up, the smoke diminishes, but never goes away completely. The engine has 5200 hrs on it. It starts instantly and makes good power. Here's how it looks right at start-up:





And after running for a few minutes:





I'll use this thread to document the steps I have taken and will take to address this problem. Comments appreciated!

[jt11791]

Don't know why this photo did not appear in the first post

[rbk]

Check timing(if possible), injectors and valve clearances and of that doesn’t do it, start thinking about taking the head off for a valve job. Out of curiosity I looked up the manual and there’s pretty good instructions.

[daletournier]

There are threads already written on this. It's seems normal, I don't know why.

Dock head has looked into it in depth.

Mine smokes also, maybe not as much as in the photo. I've looked at several doing exactly the same.

Mine starts instantly, uses very little oil and something I do not understand is the oil never gets black, always looks good.

[MartinR]

Looks like unburnt Diesel fuel. If the temperatures were reasonable cold when you took the pictures, this could be normal. Is there any smoke when the engine is under load?

[skipperpete]

Does your engine have the coldstart option in the intake manifold? The DTE has a lot of cold pipework and an intercooler that the intake air needs to get through and arrives in the combustion chamber quite cool which could cause a smoky exhaust. Try the preheat if there is one and see if that clears the smoke. What's the ambient temperature at the boats address?

[Cpt Mark]

In a class for small marine Diesel engines. Instructor said last week, diesels smoke especially on start up. It's unburnt fuel and normal. The huge amount of startup smoke should clear up after a few minutes. ALL diesels smoke. He's only been working on them for 46 years. A little smoke after the initial stream art is normal. Can't see your 2nd photo. I wouldn't worry about it.

[Yellowjacket]

What rpm do you cruise at, and what's the maximum rpm in the manual for that engine?

[Yellowjacket]

Originally Posted by daletournier

… and something I do not understand is the oil never gets black, always looks good.

I've never known a diesel that didn't blacken the oil after a fairly short period of time.

[01kiwijohn]

From the picture, it looks more like oil smoke to me. My experience has been that some engines smoke more than others, from new (remember the old Detroits?). These Yanmars usually don't smoke that much however, you've got 5200 hours on it so I'd expect to see a little valve guide wear and valve stem seals that are less than perfect. What then happens is that, after sitting for some time, a little oil will seep down the valve stem and it takes a little while, after start up, for this to burn off. It looks a hell of a lot worse than it really is. If it settles down, and the engine otherwise performs as it always has, I wouldn't worry about it.
One thing I have found though, is that most owners ignore the recommended injector service intervals. As a compromise, I advise owners to have the injectors tested, ultrasonically cleaned, and pressures re-set, about every 2,000 hours. It may not make much difference to your smoke, but it will insure that each cylinder is burning evenly and cleanly, reducing oil dilution and sulphur accumulation, thus extending its' life.
Let me know if I can help you further.

[Cpt Mark]

Originally Posted by Cpt Mark

A little smoke after the initial stream art is normal. .

That's start up, not stream art. Love autocorrect lol.

RPM's. All small diesels can run at 3200 rpm max pretty much until they die. They are designed for this and limited for higher rpms via the governor. Do you want to run them that high? You will go a tiny bit faster but burn a lot more fuel.

[Bluebeard]

I've always understood that white smoke is oil, and black smoke is unburnt diesel.

[DeepFrz]

Could be unburned fuel but could be moisture in the fuel as well. Check your filters to see if there is any water in the bowls. Also as the folks above have said could be from a cold start and if there is lots of humidity in the air it can look like that.

[a64pilot]

Blue smoke is oil, and it smells like oil and it doesn’t dissipate much either.
Fuel vapor is whiteish, stinks like fuel, sort of acidic / sulphuric smell that burns my eyes, it also dissipates rather rapidly, a little like steam does.

The Smoky Yanmar’s have an apparently slightly less than perfect combustion chamber, probably not as much swirl to mix the fuel well and they do smoke.
I have found that with my older non turbo Yanmar that a good Cetane improver does help, but not completely eliminate the smoke and greasy rear end on my boat, they are both either unburnt oil or fuel.

Higher Cetane fuel burns quicker and more completely, it also theoretically gives better performance and economy, I say theoretical cause if it does, it’s so slight you’ll not be able to tell.

[Dockhead]

Originally Posted by jt11791

My Hylas 54 is equipped with a Yanmar 4JH3-DTE turbo-diesel which makes an embarrassing amount of smoke on start-up. After it warms up, the smoke diminishes, but never goes away completely. The engine has 5200 hrs on it. It starts instantly and makes good power. Here's how it looks right at start-up:





And after running for a few minutes:





I'll use this thread to document the steps I have taken and will take to address this problem. Comments appreciated!

Just exactly like my 4JH3 HTE, down to the color of the smoke, and everything.


There are a couple of threads on here about my experiences; you might want to look them up in the archives.


I never figured it out in almost 10 years of ownership. Seeing yours, doing exactly the same thing, adds weight to one of the theories, which is that they just do that. This was the theory, by the way, of the eminent surveyor and diesel engine expert I hired to opine on the matter, when I was buying the boat.