Yanmar 6lya-stp black smoke

[Antonio micula]

Hi everyone …I am new on this forum…i would really appreciate a lot if i could get some suggestions in order to solve problem with my Yanmar 6lya-stp 370hp.

I am owner of 33ft semi displacement boat located in Europe-Croatia.

Recently i installed used yanmar engine with 1100 working hours. Proppeler size is 21×26 and according to calculation it should not be to big to cause over-propping problem.

Black smoke starts at about 1700-1800 rpm.
(I have checked yanmar rpm meter accuracy with manual tachmeter and found out that is showing about 70 rpm more).
Max rpm under load is 3030. Max rpm at idle is 3630.
At exhaust i can see black liquid diesel and black smoke.
What is really strange is that black smoke is stopping at max rmp at about 3000.

So far i have replaced all 6 nozzles and calibrate them properly to 260bar.
Intake and exhaust valves clearance was adjusted by service manual to 0.1 and 0,5 mm.
Engine working temperature is OK , about 70-80 degrees Celsius .
There is no excessive smoke at blowby.
Cold Engine compression is same at all 6 cylinders about 16-17 bar.

Pressure at exhaust elbow is 0 bar(is this normal)?measured with 6 bar scaled manual gauge.

Boost pressure is as follows : 2000rpm – 4psi , 2200rpm-7psi , 2700rpm – 14.5psi , 2800rpm – 20psi , 3100rpm-30psi.(by yanmar rpm gauge).

I have noticed that fuel limit bolt on governor was readjusted by someone before because there was no lock wire , i tried to turn this bolt little bit for testing and i could get rpm increased to 3400 but this didn’t help to reduce black exhaust .

I have also noticed that boost compensator bolt doesn’t have lock wire on it. In the service manual is described procedure to reduce black smoke by readjusting boost compensator but this also didn’t help.

If engine is overpropped would it started to smoke at 1700rpm allready? Black smoke and black liquid(raw diesel) is really a lot.

Please help with some suggestions

Thanks

Topic

[Antonio micula]

Thank you for reply

Let me try to explain because i dont want to look like i am making up stories.

I did not have prop done again but this time boat was lighter for about 350 kg or 800 lb and turbo was overhauled.

Video is done recently when boat is lighter and after turbo overhaul and there is still a smoke. Max rpm in this conditions is 3430rpm.
However i did check max rpm with loaded boat (like before when max rpm was 3330)and it went up to 3370 ,what is telling me that i get about 40 rpm after turbo overhaul.

Why i did turbo overhaul?
When i was leaving home for a work i found mechanic and told him to remove fuel pump and send it for repair. Well , when he came on boat(i was already gone) he decide that turbo is bad and that he want to try with turbo and intercooler overhaul first.
I tought OK…it can not hurt…and is cheaper…if it doesnt help we will do pump

So,when i came back home(after 1 month)….mechanic has installed back turbo and intercooler….we did test run with lighter boat…result is that i can almoast reach required rpm but smoke is still there?!!!?

What to do…what to think?

Just to mention that any mechanic i have been asked to remove fuel pump was not happy or confident about that job. Conclusion is that is not easy to find really good mechanic,at least here where i live.

And to mention….sudden stopping problem was dirty fuel problem….i have cleaned pre-filter and replace filter and no problem since…

Sorry for long post but i hope things are more clear now…

[Rob Schepis]

As best as I can tell in that fuzzy pic, the turbo looks good. That black smoke in your video should not be there.

Originally you had the prop pitched back which got you up to ~3350rpms. Now you are reporting 3,430 – did you have the prop done again?

You said the intercooler was cleaned. Does that mean removing the core and cleaning the air side 100% spic and span?

With the unknown history and the fact that the pump settings have been messed with it may be prudent to look into where you can send the pump out for re-calibration?

Yanmar Aftercooler Maintenance

[Antonio micula]

anybody?

I have hit a wall here…what to do ?

[Antonio micula]

video

On the above link it is possible to see how does it look like when I am running.

Until about 35th second of video engine is running at about 2750 RPM , after that it is about 2500 RPM.

I would appreciate if i could get opinion is this colour and amount of smoke acceptable ?

[Antonio micula]

According to company that did turbocharger repair no any major faults was found.

[Antonio micula]

Yes I did say that I will post picture and I am sorry i didnt . Unfortunately nature of my job is that i travel a lot and i don’t have enough time to spend on my boat so i just let mechanic to take off turbocharger and send it for repair . I tought it can not hurt. The main thing is that this engine is used and i dont know real history so every maintenance is welcome. I forgot to mention that intercooler was cleaned as well .

Below are photos that i took at that time when i promised that i will post them , but i was dragged to something else.

[Rob Schepis]

Antonio micula wrote:

…..I will post turbo photos later when i get to PC. …….

Based on your above statement from Aug 4th it appears you already have the pics just have not posted yet ?

[Tony Athens]

On Aug 4 I asked to see inside your turbo

?????????????????????????.

Tony

[Antonio micula]

More testing

Hi all

After some time i did more test runs.

Just reminder about engine :

Turbocharger hes been sent for reparation.

We have replaced all 6 nozzles and calibrate them properly to 260 bar.

Intake and exhaust valves clearance was adjusted by service manual to 0.1 and 0,5 mm.

Engine working temperature is OK , about 70-80 degrees Celsius .

Propeller has been sent for correction and now i can reach 3430 rpm.

There is still some black smoke coming out exhaust (and black liquid), starting at 2100 rpm and the worst is at 2500 rpm.

At 2700 rpm black smoke is changing to black and white smoke (like vapor), at this time boost is about 1 bar (14.5 psi).

What I am not sure is how much black smoke is normal ? After all this work at engine , amount of black smoke is much less but it is still there , and not only when accelerating but also when running constantly (especially at 2500 rpm).

Please note that same boat as mine with 280hp Iveco engine is got same max speed (21kts) as I have with 370hp yanmar?

Attached photos are showing smoke at 2700 rpm.

[Tony Athens]

If you are sending crud to the ON-Engine filter to where you are finding it there, you need to IMPROVE your PRIMARY off-engine filtration system..

I’d say you are playing with fire..

Tony

[Antonio micula]

Hi

It just happend half hour ago again….It is was not shut down completely….just rmp drop down by itself….from 2600 to app 800…it took like 20 sec to rev up again……the other day happened diferent thing…I lowered down by command rpm from 2500 to app 1300 and engine shutdown byitself…..in both cases it looks fuel reduction….in fuel water separator i have noticed dirt…
Maybe I need to change diesel oil filter

[Rob Schepis]

Read this “shutdown/slowdown” issue several times and do not really understand what is happening….Is the engine actually shutting itself off, like someone is turning the key off or hitting a stop button? If that is the case check the relay that control the shutdown solenoid as well.

[Tony Athens]

Sudden RPM drop———-Until I “see” your engine especially the injection pump, throttle linkage and fuel solenoid, can’t really comment..

Tony

[Antonio micula]

Tony

Yas i did check tach accuracy and is reading 70 rpm more…since it is reading 3400- real engine rpm is 3330.

I will post turbo photos later when i get to PC.

What do you think why engine is sometimes shuting down when i am sudenly slowing down…for example from 2000 rmp to minimmum rpm?

[Tony Athens]

#1—————-Have you verified tach accuracy at 3000 RPM in neutral AT THE DOCK– Yanmar tachs typically read close to 100 HIGH in the higher ranges, meaning your current 3350 is maybe 3250-ish.

#2–Regardless, you are still over propped–Until you can reach a solid / accurate 3450+, you will not get rid of the smoke, you are hurting your engine and you are leaving usable power on the table

#3–I want to SEE inside your turbo–Sorry, but until I see it, believe me, you are not sure what is going on..

Tony

[Antonio micula]

thank you for reply

Hi guys

I have update….propeller is changed as per calculation from 21 X 26 to 21 X 22.

I did get 400 rpm more and now max rpm is 3350.(unfortunately not 3450)

Black smoke is significantly less but it is still there. Black smoke is starting at 2150 until 2750 – it is less then before but you can still see it.

Lets say I am happy comparing how it was before.

However the other problem what i have experience is engine shut down when fast lowering rpm from about 2000 to minimum rpm (it happen twice).

Just reminder my boat is semi-displacement hull and it is not going easy to plane (maybe this should be taken in consideration)??….i did check turbo and no signs of rust….i did check back pressure it is almost 0 psi.

Thanks a lot for your help it means a loooot to me.

Toni

[Tony Athens]

What did I read wrong? I thought you said you were making 3030? 300+ short or are you now 500+ short.. And your numbers need to be REAL——-NOT Yanmar tach readings………

I can only go by what you post..

Tell him what you have and tell him you want 3450+.

As to your pump, I would have no clue what has been messed with..

Got good pics of the screw or screws you or ?? has messed with?

Tony

[Bill Desmarais]

toni,

If you believe the engine is really over propped by 500 rpms then simply ask the prop shop to change the 21X26 prop to a 21X21 square. That should free up 500 rpms to get you to 3400 +-.WOT.

Reduce the prop pitch by 5 inches.

Keep us posted.

Regards, Bill D

[Antonio micula]

Tony

Thanks for reply….i have already book a crane for tomorow lift so i can remove propeller and send it for readjusting.
The only thing to clarify is how many rpm i am missing….i could see that with fuel limit i can adjust rmp and now i am not sure how was factory set.
When i did first test run max rmp was 2900 so i think that should be my reference point even do somebody was readjusting this bolt before i bought this engine.
Do you agree that in that case I am 500(or even 550) rpm short and that is what i have to say in propeller shop before readjusting?

It is not simple or cheap operation to remove propeller, that is why i want doublecheck before sending propeller away.

Thank You very much for your help.

[Tony Athens]

#1 is this————————I personally know this exact engine like no other as I not only work on on them from from time to time on local vessels, I installed a pair of them in my Bro’s vessel in 2005.. He put well over 10,000 hours of them in the following 8 years before we re-powered…At that time the engines were still in EXCELLENT CONDITION………Very good engines and compare favorable with any Cummins B in most applications although they have a few things about them that require a tad more due diligence to keeping them in 1st class shape..

With that said——–Listen to me carefully and throw out everything you said referencing your perceptions about 1700 RPM, the boost compensator, boost numbers, etc , and absolutely quit “fuc…..ing” with the stop screw on the pump–In fact, you may have to have that reset professionally—————————-not sure at this point……………..

Are you ready to listen? If yes, then this is the only solution..

Do this and do it without question……………..Take off your prop, take it to a 1st class shop and tell them this, and this only………..You are a solid 300 RPM SHORT and adjust accordingly.. They will ask you all sorts of things, like HP, vessel weigh , vessel speed at WOT, the engine rating, etc etc………………….. But you need to know, NONE of this matters–what matters is this engine in YOUR VESSEL operating under those conditions ( not some book) needs to see OVER an accurate 3400 RPM in YOUR VESSEL and see it easy under the worst case conditions————————-That is IPPSO FACTO…………….And, 100% FORGET the numbers on the engine data tag–

If he asks to the engine power–tell him this, nothing else—-350 SAE BHP at 3450 RPM ..

Do this and then your base issues with GO AWAY……………….You are are seriously or GROSSLY OVER PROPPED and you have already wasted 100’s ( maybe 1000’s) of dollars either using you own diagnostic methods, or listening to others with no clue.

It’s now 100% on your plate now……………… But do take notice of this too_… I am not trying to sell you anything.. I really doubt has been been that way in that past from the “others” that have been guiding you.. Something else to ponder as you decide whether to question my response when I say a “solid 300 RPM short”..

Tony

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