Causes for gray smoke

[Waterant]

Hi guys,

I can use some help to troubleshoot darer gray smoke from the exhaust on a new to us 41' trawler.
Engine is industrial Yanmar 145hp with a turbo born in 1987
When transmission is not engaged, I can give it a throttle to 2500rpm which is continuing duty Rpm for this engine and it's smooth and happy, no visible smoke.

When we are underway, anything over 1500rpm causes gray smoke and I did not try 2000 or over because the smoke does not look right and getting worse with more throttle and I can feel vibrations are increasing.

Am I correct assuming the engine is overloaded?
Maybe by incorrectly sized prop?

Can a missaligment in the shaft causes the overload?

Can it be a turbocharger not working correctly under the load or it engages with high rpm regardless of the load? I know nothing about turbochargers - this is a new kind of animal to me.

Anything you recommend to check first?
We are in the remote areas of Nova Scotia now and access to a mechanic is limited.

Thank you

Anton

 

[Lepke]

Black smoke - It could be over propped. but it sounds like the air fuel mix isn't correct. And that can be anything the puts too much fuel into the cylinder. Burned injector tip, turbo issue, restricted air intake, etc.
If it's blue smoke, that indicates oil burning - bad rings, worn cylinder, leaking valve guides, diesel in the oil, oil in the diesel, turbo leaking oil into the intake, and others.
It's easy to check alignment, loosen the coupler bolts and check the gap with a feeler gauge all the way around. If there's a too big gap at the top, the front of the engine needs to rise. Gap on the left, engine front needs to go left, etc. I do alignments to .002".
I'd call a major prop dealer with engine, transmission and current prop info and see what they say.
The turbo is controlled by the exhaust, but not designed for high rpm, no load. A failing bearing can cause turbo drag, less air, black smoke. If the engine has a lot of sludge buildup, the line to the turbo is one of the first places that get restricted oil flow. Low oil flow = bad turbo bearing, then bad seals, then oil in the intake, then turbo failure.
You gotta keep the oil clean in a turbo engine.

 

[ghost]

Your getting good advice, so I’ll hit and run with a lucky guess. 1500 rpm is near the magic transition point where the turbo would start to matter. If you kept increasing throttle without further significant rpm increase and the smoke went from dark to black to streamers of carbon I’d jump right to the conclusion that air was not keeping up with fuel. That is the job of the turbo.

Could be other things, but it would be on my short list to check first.

See what the blades look like, if they are clean or coked up. See if it spins easily.

 

[Cigatoo]

My guess would be that the turbo is not spooling up or you are losing boost pressure. You will get rated rpm with no load if the turbo is weak or not spinning at all. With a load on the engine (in Gear) you will get smoke and much less than rated rpm. Check hoses from turbo to manifold to be sure there are no leaks. Look for split hoses, loose clamps, and the like.
You didn’t state the make of the boat but some of the Mainship (Yanmar equipped) trawlers were known to have poorly designed exhaust systems causing seawater to back flow into the turbo.

 

[Waterant]

Thank you for your reply.
Oil was clean and I replaced the oil and filters recently.
I do not think turbo was serviced in 10 years or so.
Is there any temporary fix I can do until I get to civilization and have time to remove and clean it?
Some turbo cleaner spray maybe?

 

[greysailor]

Thank you for your reply.
Oil was clean and I replaced the oil and filters recently.
I do not think turbo was serviced in 10 years or so.
Is there any temporary fix I can do until I get to civilization and have time to remove and clean it?
Some turbo cleaner spray maybe?

Pop the air filter off and see if the turbo will spin freely with a socket and extension on the intake nut....might just be a little carbon/rust on the exhaust side blocking the blades. If you can't turn the extension by hand (no ratchet wrench), you'll need to pop the exhaust elbow off and clean the exhaust housing with PB Blaster, small screwdriver and vacuum until the blades will turn freely. Common problem on marine turbos that don't get run often.
Good luck!

 

[ghost]

If the blades don’t spin easily, well then you can run the boat at naturally aspirated speeds and just go slow for awhile. If they do, but are not clean, then you can clean them manually or you can even get the turbo spooled up a bit and spray some soapy water into the intake until it sputters a bit, then repeat. Personally, my guess is your beyond the spritzer solution and I fear you are going to find that the bearings are toast after sitting for a long time. Not my specific engine of experience, so can’t speak at all to what’s common to find on your engine.

I’ve gone long distances with a bad turbo, get used to trawler speeds!

 

[Waterant]

Hi guys,

> If you kept increasing throttle without further significant rpm
> increase and the smoke went from dark to black

it never go to black, just thicker gray on higher rpms.

I checked RPMs with a mechanical tachometer and the gray smoke actually starts around 1900 RPM in gear and because we traveled mostly at 1700 RPM for better fuel consumption, the smoke did not bother me much after that.

I took out the air filter, checked the turbo - it's super clean, looks like new and spins easily. air filter on the turbo is clean.
exhaust piping was replaced not too long ago but I did not check the condition inside yet - it's on the list.

injectors were replaced recently but i will take them out to check,
will i see a burned injector tip or it has to be taken to a specialist to disassemble?

anything else I need to check?

Also, maybe it's related, i noticed oil pressure gauge shows normal oil pressure 30-40 PSI on startup (when the low-pressure buzzer stops) but after some time running it goes to something like 5 PSI constant for the whole trip. there is no low-pressure alarm buzzer sound so i always assumed the problem is with the gauge or the wiring from the pressure sensor is getting too warm and increasing the resistance causing a false voltage sent to the gauge. i am planning to add a T and install a mechanical gauge on the engine to verify the oil pressure.*

can it be related to the gray smoke problem (like not enough*oil getting to the turbo)?

I apologize*for the log post and thank you for time in advance.

 

[Lepke]

If the engine is in good condition (good compression) my first guess it's over propped. I don't know Yanmars well, but diesel fuel injection is controlled by a governor usually built into the injector pump. When you advance the throttle you're really changing the speed setting on the governor. It causes more fuel to go to the injectors. When the engine reaches the speed setting the fuel is reduced to maintain the speed setting. If you're getting black smoke, the pump is supplying more fuel to maintain the speed setting than normal. It also means you're asking the engine to supply more hp than it was designed to give. The only other common reason for black smoke is the air fuel ratio is wrong. Too much fuel, not enough air. That can be from some air restriction of intake air - not enough engine room vents, dirty air filter (most marine diesels, especially big ones, don't have an air filter, just a screen to keep things out). It is assumed a marine engine isn't exposed to dirt in the air like land engines. The other cause for air restriction is the turbo turning slow because of a dragging bearing or an exhaust restriction that slows the exhaust leaving, hence not turning the turbo fast enough. The exhaust at high rpm spins the turbo so anything restricting the exhaust slows the turbo. Like a muffler too small, small exhaust hose, partially plugged exhaust elbow, too much water in the wet exhaust.
If it's blue smoke it's oil getting past the rings, bad valve seals, or a leaking turbo oil seal. bad rings show up in a compression test.

 

[fgarriso]

Gray smoke may be from water in the cylinders.

It could have a blown head gasket or a cracked head. If I remember correctly you said that as the RPMs increase the GRAY smoke increases also. That makes sense as a coolant leak would increase as the cylinder pressures go up.
Have a compression test done with all injectors removed. If the pressures on one or two adjoining cylinders are off by 20-40 lbs. have the engine head removed to check the head and head gasket.

I hope this helps for what its worth.

 

[Waterant]

> That makes sense as a coolant leak would increase as the cylinder pressures go up.

As I understand, that would mean the coolant level going down? I did not add any coolant for the 300+ hours we put on the engine this summer and it seems to be the same level and pink color as when we started so hopefully this is not the case.
I'm planning to do the compression test anyway.

as I can see from the replies, the most likely causes:
- i'm over propped or
- partially plugged exhaust elbow

i guess the compression test and disassembling the exhaust for inspection will confirm or deny this.

> If the engine is in good condition (good compression) my first guess it's over propped.

What would be my options if I'm over propped? Getting a new prop or ignore? at 1700 RPM the boat is doing 7.5 knots fully loaded, the engine is happy and the fuel consumption is relatively low (2GPH). maybe it was done on purpose for some reason and I should not worry about this because it worked fine for 30 years?

Thank you

 

[FF]

' will i see a burned injector tip or it has to be taken to a specialist to disassemble?"

If you do remove the injectors, most shops will check them for free or $5.00 each if they get the work to rebuild them.

"What would be my options if I'm over propped? Getting a new prop or ignore? at 1700 RPM the boat is doing 7.5 knots fully loaded, the engine is happy and the fuel consumption is relatively low (2GPH). maybe it was done on purpose for some reason and I should not worry about this because it worked fine for 30 years?"

The usual rule of thumb is if you cruise 10% RPM below where black overload smoke begins you are NOT over propped.

I would carry on as is for the next 30 years..

 

[sunchaser]

Does the engine have an after cooler?

 

[Waterant]

> Does the engine have an after cooler?

No aftercooler.

 

[MYTraveler]

It seems to me that there are four possibilities (or some combination thereof):
1. Blue smoke indicates burning oil. And idling two-stroke gas motors with pre-mixed fuel is the best example of this.
2. Steam, which is white and normally dissipates quickly, but in the right atmospheric conditions may linger like fog.
3. Black, which is the result of incompletely combusted diesel. The best example of this is an old bus under heavy acceleration.
4. Normal combustion. Modern engines don't emit much visible exhaust when running properly, but older engines do -- that looks grey.

It sounds to me like you have black exhaust, just not a lot of it. That happens from two things -- a bad injector that is not properly atomizing the fuel, and too much fuel relative to the oxygen. The too much fuel can result from either a bad turbo (which doesn't provide enough pressure (oxygen) to assure complete combustion, or overloading.

 

[Waterant]

thanks, guys. I will disassemble exhaust to check if there is any build-up which can affect the turbo efficiency, take out injectors for inspection and check the compression. it will give me some data to work with on the next step. I'll update this thread with my findings for a reference if somebody else will have the same issue.

 

[Tom.B]

Hi guys,

I can use some help to troubleshoot darer gray smoke from the exhaust

We get gray smoke at the top end of the rpms when we have growth on the props. For us, it doesn't take much at all. Even as low as 5-10 barnacles on the blades. If yours has been fine for years, it is unlikely you need to re-pitch your props. something changed and it sounds like you have covered the expensive stuff already. Just make sure your props are spotless and your fuel is clean before you go chasing things like injectors, coolant leaks, valve jobs, or crack in the heads.

 

[SeaBreeze]

Heavy steam can look grey... It happened on my boat during sea trial at higher rpms. In my case I went after the raw water system and found old impellar bits, mud, and old pieces of zinc in the heat exchangers. Once all that was clear and a new impellar, it was gone. She still steams but it is white and not excessive. I'd look at the easy stuff first before pulling injectors, etc.

 

[Waterant]

Thanks for the tip. The boat is already on hard and prop was as clean as on the day we dropped her in the water in May. This is the first summer I have this boat and not sure if this is a new issue. When I started this thread, the tachometer showed as little as 1500 RPM when we started getting visible smoke which got me alarmed. in reality, this was 1800-1900RPM (tach died completely by the end of the trip). I installed and calibrated with a laser handheld tachometer a Nmea 2000 integration which takes RPMs from the engine and another one from the alternator and was getting precise readings for the rest of the trip and kept RPM around 1700 with no smoke. The previous owner cruised around the same RPM so smoke probably did not bother them.

> In my case I went after the raw water system and found old impellar bits, mud,
> and old pieces of zinc in the heat exchangers.

You read my mind. this is on top of my to-do list. I did not think of it as a cause for the smoke because this does not affect fuel/air ratio but a good thing to do anyway and if that fixed your smoke issue, even better.

as I understand, I should not see any smoke on a warmed-up engine even at higher RPM as long as it's not getting into the overloaded territory and this engine is rated at 2800RPM continuous duty so the smoke starts around 70% of rated max RPMs.*It may be just a case with over-propping which I will not worry about but I want to be proactive and check/fix the possible causes outlined in the (much appreciated) replies I'm getting. I have a few boring months before the next season and removing injectors and disassembling the exhaust is within my limited abilities anyway

 

[C lectric]

Grey smoke can be from two sources:
----actual overfueling in one cylinder from a goofy injector. THis usually results in a STRONG smelling ,nose grabbing odour. That trail will carry long past the boat transom.
----steam from a lack of raw water flow. THis will dissipate fairly quickly often with in 50 or so feet. It may smell of exhaust but not that nose grabbing odour.

To me it sounds more like you have a problem in the cooling system causing poor raw water flow, thus poor cooling, as the engine comes under higher power. At low power levels the cooling is adequate but not so as the power asked for is increased.

Below I have linked my tome which covers a lot of the causes of the poor cooling from restricted raw water flow. Read it through and if there are questions arise then ask. You should get help.

Pat attention to SeaBreezes comments.

 

[SeaBreeze]

Does your gray smoke look anything like this? This is how dark my steam was before I cleaned out the heat exchangers. It can get pretty dark gray if it gets hot enough.

 

[Waterant]

great, thanks. this would explain why cleaning the cooling system helped SeaBreeze with a similar issue. and I did not notice any strong odor and the smoke/steam dissipated in a few feet after the boat. I'll get with cooling system cleaning as the first step.
maybe this also explains the high engine room temperature which looked a bit high to me (around 120F after an hour or two of running at 1700RPM) but the water temperature was always in the green zone so i did not pay much attention to it.*

 

[Waterant]

> Does your gray smoke look anything like this?

the same color but probably only 20-30% of the volume in your photos after 2200RPM