Smoky Yanmar

[Dockhead]

My 4JH3 HTE has smoked since the day I bought my boat 8 years ago.

I almost refused to accept the boat as a result of the smoking. I made the seller go to great lengths to try to stop it -- including sending the turbo off for a rebuild, sending the injection pump off for bench testing, etc., etc., etc. I finally accepted the boat after a really good specialist engine surveyor told me that the engine was fine and that Yanmars just "tend to smoke".

Since buying the boat, I replaced all the injectors for new, and have had the injection pump off again for bench testing and then timing upon reinstallation.

Nothing has changed anything in the least.

The engine runs like a top, smooth and sweet, has normal fuel consumption, and starts if you so much as look sideways at the ignition key. I've never needed the preheater even in below freezing weather and I'm not even sure it works. Had 830 hours when I bought it and nearly 3000 now. Oil consumption is normal and has not changed since I bought the boat -- maybe a liter in 100 hours, which means I usually don't add any oil between changes.

But the smoke bothers me!! Over the last 8 years I have observed other boats with Yanmars and have not seen such volumes of smoke out of any of them.

The smoke is grayish, so would seem to be fuel. Since there is no significant oil consumption, that would seem to confirm that the smoke comes from fuel. The smoking is heavier when the engine is cold; less after it's been warmed up really well, but always present.

But the injectors were replaced without changing anything, and the injection pump has been bench tested, at great expense, twice, with flying colors. The timing has been set by the Yanmar main dealer -- twice.

So how can it be fuel?

The turbo was rebuilt once, and I have inspected and cleaned it from time to time. It never has much carbon on it and always turns smoothly. A couple of years ago, I had all the of the coolers -- main heat exchanger, engine oil cooler, trans oil cooler, and charge air intercooler -- professionally cleaned and inspected. After spending a lot of money on that, the pro said -- they were all clean as a whistle; the work was unnecessary


The Yanmar dealer told me that perhaps the bores are polished. But how can that be? That would mean higher oil consumption, wouldn't it? And reduced compression which would mean hard starting -- I have none of these symptoms.


I'm not really hopeful of finding any solution to this after all these years and hours, but thought I would throw this out in case someone has some ingenious idea.

[moguzhanoguz]

Where does it smoke ? Exhaust ?

[Dockhead]

Originally Posted by moguzhanoguz

Where does it smoke ? Exhaust ?

Yes, from the exhaust.

[jimbunyard]

Does the exhaust leave soot on the transom? Have you thought about trying a hotter thermostat? Are you sure that the injectors are correct ones for your specific engine?
(maybe an inter-model, un-notified spec change?)

[skipmac]

Have you tried smelling the exhaust to see if it smells like fuel? I have had boats with an old smoky engine with a fuel problem and the exhaust had a noticeable diesel smell.

[Sailmonkey]

The thermostat could be the ticket.

Do you have an IR thermometer? What is the temperature of the thermostat housing?

Does the engine smoke when well loaded and running hard/hot?

[moguzhanoguz]

Originally Posted by Dockhead

Yes, from the exhaust.

Could it be steam rather than smoke ? If yes then you should check the exhaust elbow. One of my friends had the same problem and solved by changing elbow with stainless steel one.

[sailorchic34]

Assuming that the injection pump and injectors are perfect and injection timing is perfect, I would be looking at the injection limiter adjuster. The injector limiter is part of the governor. Think of it as a mixture control. If it's too rich the exhaust will smoke some. If too lean, BAD things will happen. It's far better to be a tad rich then a tad too lean. Specially with a turbo.

The trick is to adjust it till then engine smokes just a tad and call it good.

The injection limiter is normally adjusted and set (and sealed) at the factory and is not normally a user serviceable item. But it can be adjusted. Don't ask me how I know....

Just know that going to lean could cause engine failure.

[donradcliffe]

Thanks for the post. I've put about 200 hours on a J4h3-te in the racing boat Merlin this year in the course of 4 deliveries, and I'm getting familiar with the engine. It has about 1250 hours on it, and consumes less than half a liter every 100 hours. No visible smoke at any time, and it starts immediately.

One of this week's projects was replacing the temperature sensor. The old one would read nearly 100 C under normal operation, but I didn't believe it after hitting the engine with an IR gun. Finally took the sensor out and put it in a pan of hot water--it read a consistent 30-35 C high. Yesterday in installed the new sensor, which had a resistance of about 200 ohms higher than the old one. A quick check at the dock (high idle in gear) had the temperature gauge reading 60 C, which seems a bit low, but I prefer it to 95 C. I'll know more next week after I deliver it up to San Francisco again.

My understanding of the oil change schedule is 250 hours--after 100 hours the oil looked clean and new. After 200 hours, its looking a bit dirty, but not bad, and I plan to change it next month.

The only problem I have had was loss of power on the return from Hawaii, and thanks to Dockhead's suggestions, changing both fuel filters cleared that up. The boat will now easily reach 4000 rpm at the dock, because the folding prop is a bit undersized, for less drag.
The boat was on the Great Lakes for most of this engine's life, and the lack of rust on an 8-10 year old engine is pretty amazing.

[a64pilot]

It could be bore polishing, which means it would be oil of course.
One way to polish bores is from an engine that is not used often, it sits and over time forms a slight layer of rust on the bore, then is run and the rust is of course very quickly worn off, do this several times and the bore cross hatching is gone and you have bore polishing. Lots of small airplanes suffer from bore polishing, the only cure is honing the cylinders. If it's excessive it will cause oil to go very dark exceptionally fast from all the blow by and will even cause excessive oil temps from the hot blow by.
It is different from bore glazing, glazing is when you get a glaze that fills the cross hatches, glaze can come from unburned fuel and not reaching operating temps over time.
If it's a direct injection Diesel, the bores can be inspected with a bore scope, this is what that tool is designed for of course, but It's like a multimeter sort of, meaning that it has many other uses. Once you have one you may use it more than you thought you would. Very good ones that plug into a laptop can be had now, much less than they used to be.

In my opinion you cannot change the mixture ratio of a Diesel.
A Diesel of course has no throttle valve so it always takes in a full lung full of air, it is never choked off, it is leanest at idle of course, then to accelerate a Diesel all you do is add fuel and the mixture becomes richer.
Anything you do to enrichen the mixture will cause a Diesel to accelerate, fuel not air and fuel mixture is what controls engine speed.

[model 10]

Don't mess with the inside of the pump, that is for the pro's.
You probably need to adjust the timing. It's not a big deal, a degree maybe. So far everybody has installed the pump in the factory position and they tell you it's perfect. It is for most engines but some run a little different and need the pump timing adjusted just a bit for peak performance. Apples and pears but the Perkins manual mentions this, maybe for hot rod taxi's

[Dockhead]

Originally Posted by a64pilot

It could be bore polishing, which means it would be oil of course.
One way to polish bores is from an engine that is not used often, it sits and over time forms a slight layer of rust on the bore, then is run and the rust is of course very quickly worn off, do this several times and the bore cross hatching is gone and you have bore polishing. Lots of small airplanes suffer from bore polishing, the only cure is honing the cylinders. If it's excessive it will cause oil to go very dark exceptionally fast from all the blow by and will even cause excessive oil temps from the hot blow by.
It is different from bore glazing, glazing is when you get a glaze that fills the cross hatches, glaze can come from unburned fuel and not reaching operating temps over time.
If it's a direct injection Diesel, the bores can be inspected with a bore scope, this is what that tool is designed for of course, but It's like a multimeter sort of, meaning that it has many other uses. Once you have one you may use it more than you thought you would. Very good ones that plug into a laptop can be had now, much less than they used to be.

In my opinion you cannot change the mixture ratio of a Diesel.
A Diesel of course has no throttle valve so it always takes in a full lung full of air, it is never choked off, it is leanest at idle of course, then to accelerate a Diesel all you do is add fuel and the mixture becomes richer.
Anything you do to enrichen the mixture will cause a Diesel to accelerate, fuel not air and fuel mixture is what controls engine speed.

I have a cheap borescope. Maybe I'll pop an injector out and have a look.

But how could it be polished bores and oil smoke -- if the engine doesn't consume oil? Doesn't seem to make any sense to me.

[Dockhead]

Originally Posted by Guy

Don't mess with the inside of the pump, that is for the pro's.
You probably need to adjust the timing. It's not a big deal, a degree maybe. So far everybody has installed the pump in the factory position and they tell you it's perfect. It is for most engines but some run a little different and need the pump timing adjusted just a bit for peak performance. Apples and pears but the Perkins manual mentions this, maybe for hot rod taxi's

Thanks. Maybe this is worth checking. Can the timing cause this kind of smoking?

[Kenomac]

Dockhead,

We have the same Yanmar engine, same model year, and ours does not smoke. It used 1/2 liter of oil over a 125 hour period. When was the last time you cleaned or replaced your foam air filter. I understand the foam breaks down over time and can clog the filter, causing the engine to run slightly rich and smoke more than normal.

I hope this post doesn't offend anyone on cf, it's not intended to be derrogatory in any way towards the owners of Yanmar engines, diesel motors which have air filters, or anyone who may intend to purchase a diesel engine sometime in the future.

[Dockhead]

Originally Posted by Kenomac

Dockhead,

We have the same Yanmar engine, same model year, and ours does not smoke. It used 1/2 liter of oil over a 125 hour period. When was the last time you cleaned or replaced your foam air filter. I understand the foam breaks down over time and can clog the filter, causing the engine to run slightly rich and smoke more than normal..

Hi Ken:

Mine doesn't have an air filter at all -- just a metal sieve.

But this is a hot tip I think -- a restriction of air flow could of course cause smoking. I'll check it.

My 4JH3 HTE also uses very little oil, less than a liter between changes. Which makes me doubt that it is oil smoke. I've had healthy engines which used more oil than that.


Off topic, but bless Yanmar for making engines which don't leak a drop of oil. What a luxury compared to the old Perkins in my last boat! I used to put diapers under it!