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  • #21316

    Antonio micula
    Participant
    Vessel Name: pilotina
    Engines: yanmar 6lya-stp
    Location: europe
    Country: Croatia

    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

Viewing 20 replies - 1 through 20 (of 40 total)
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  • #39021

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    Let’s SEE your engines entire Crank Case Ventilation System…………..Just a factory hose going to ??

    Not over filled in the crank case/oil pan ? More IS NEVER better on very shallow sump HIGH-RPM Engines in a planing boat. Usually the opposite works better (running on the low mark or even a tad below) when you have possible blow-by or oil whipping issues.

    #38911

    Antonio micula
    Participant
    Vessel Name: pilotina
    Engines: yanmar 6lya-stp
    Location: europe
    Country: Croatia

    Oil in blowby

    Hi recently i have noticed oil coming out on blowby ( pls check attached photo).
    There is about 4 oz after 20 hours of engine run.
    Any recomendation?

    #28564

    Antonio micula
    Participant
    Vessel Name: pilotina
    Engines: yanmar 6lya-stp
    Location: europe
    Country: Croatia

    Back pressure

    Tony

    Finally we have adressed last problem which is causing black smoke.

    Last week after test run with bypassed muffler i have noticed that black smoke is minimized , it is remained only at 2300 – 2500 rpm but only a little bit and i would adress that to boat hull type because that is when boat is pushing biggest amount of sea.

    If i compare boost with and without muffler i can see that i can get more boost at lower rpm with less black smoke.

    And now I come to another issue and that is new muffler installation and i would need more advice about that.

    I have attached drawing to better explain which are mine limitations , and the biggest is not enough space between water line and deck where i have to install new muffler.

    I will make new riser where we will use all available height and that will be about 14″.

    1. Original Yanmar wet exhaust is 5″ , can i use same size for all system or i have to go to 6″ or more in order to reduce back pressure? Manufacture suggest 6″or even more for 370 hp.

    2.Since i have only 10″ above LWL , which type of mufller i have to use (in-line or lift ) , to get less back pressure and less noise?

    Thank you

    #27263

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    By-pass your muffler–Your exhaust pressure is crazy……….

    As to you engine and the way your vessel loads it in the 2500-2600 RPM range, that sound more like it’s a vessel vs. ” its Climbing over the hump” speed and the engine may just way overloaded at that speed.

    Tony

    #27239

    Antonio micula
    Participant
    Vessel Name: pilotina
    Engines: yanmar 6lya-stp
    Location: europe
    Country: Croatia

    Tony

    Please find attached picture where you can see bolt on the exhaust elbow where test probe was connected

    #27222

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    – Probe was installed on the exhaust elbow test port

    Never see this “test port” Send me a pic

    ~~~~~~~~~~~~~~~~~~~~~

    – He was using digital gauge..i am not sure which brand–

    No problem

    ~~~~~~~~~~~~~~~~~~~~~~~~~
    May I ask (just for my understanding) please :

    – if boost is reaching good 35 psi for the 3400 rpm does this still means that back pressure have negative effect on engine?

    – at about 2500-2600 rpm when smoke is worst , back pressure is about 70 inH2O ( still within limit) , does this means back pressure is not problem at this rpm?

    At 2600 you should be substantially UNDER the limit

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    – could I do a simple test by bypassing muffler , just temporary for testing to see does smoke goes away?

    YES

    #27194

    Antonio micula
    Participant
    Vessel Name: pilotina
    Engines: yanmar 6lya-stp
    Location: europe
    Country: Croatia

    Tony

    – Probe was installed on the exhaust elbow test port

    – He was using digital gauge..i am not sure which brand

    May I ask (just for my understanding) please :

    – if boost is reaching good 35 psi for the 3400 rpm does this still means that back pressure have negative effect on engine?

    – at about 2500-2600 rpm when smoke is worst , back pressure is about 70 inH2O ( still within limit) , does this means back pressure is not problem at this rpm?

    – could I do a simple test by bypassing muffler , just temporary for testing to see does smoke goes away?

    #27190

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    May I ask where your mechanic installed the probe to measure the back pressure? This is important . Do you know what type of gauge he used to measure it?

    Assuming all was done right above:

    The exhaust pressure limit for your engine making full HP at 3300+ RPM is 78″ H20…..For reference, Cummins has a spec of 41″, and most Cat & Deere engines are in the low to mid-30″ range………………………………My guess would be you are 100% over spec at 3400 RPM…………………Your issue is most likely your exhaust design!

    Your “custom muffler” looks very suspicious and the factory elbows are close to junk beside being inherently restrictive on their own..

    You have the to do a “proper exhaust”–Many do not..

    My brain was on a different engine–Yes, you do not have a waste gate.

    Tony

    #27153

    Antonio micula
    Participant
    Vessel Name: pilotina
    Engines: yanmar 6lya-stp
    Location: europe
    Country: Croatia

    Hi Guys

    – Finally i did back pressure measurement : at 2500 rpm – 70 inH2O
    at 3100 rpm – 118 inH2O

    – Just reminder that boost pressure at 2700 rpm is 15 psi and at 3400 rpm is 30 psi(full scale).

    – Yanmar mechanic who did measurement said that on my turbo there is NO waste gate .

    – I can reach max 3400 rpm

    #25599

    Antonio micula
    Participant
    Vessel Name: pilotina
    Engines: yanmar 6lya-stp
    Location: europe
    Country: Croatia

    – it might be connected with planning curve…my boat is pure semi displacement type….but then again , how come the other boat (same as mine) with less hp(iveco 280HP) is got same max speed and it doesn’t have black smoke….that is what bugs me

    1. I will be in chance to measure exhaust pressure in few weeks

    2. photos attached

    3. I am not sure where is it and how to check waste gate?

    4. On the last test run (video posted above) i could get 3500rpm on the yanmar tachometer , this is accurate 3430 and still you can see on video there is some black smoke….on the video I am running at 2700 rpm first and than drop to 2500 rpm

    #25547

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    Overall, a clean install although needing a new turbo at such low hours is far from Kosher.

    The fact that the exhaust cleans up at RPM’s above 3000 or so may say something about the “planing curve ” of your vessel as its current weight..

    1) Let’s get the exhaust pressure measured properly to eliminate that

    2) Because your mixer in the pic is so easy to remove, I’d really like to “see” inside your exhaust outlet of the turbo..

    3) Are we 100% sure your waste gate is not stuck slightly open? That could explain much as to dark smoke at RPM’s below 3000.

    4) And most important–Did you ever pitch down (2-3 inches) to get you loaded RPM up to over an accurate 3400?

    BTW, until you do that (#4 above) , nothing discussed above matters in this entire thread really matters..

    Tony

    #25538

    Antonio micula
    Participant
    Vessel Name: pilotina
    Engines: yanmar 6lya-stp
    Location: europe
    Country: Croatia

    and more

    #25535

    Antonio micula
    Participant
    Vessel Name: pilotina
    Engines: yanmar 6lya-stp
    Location: europe
    Country: Croatia

    here are some photos

    #25527

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    All testing other than RPM certification must be taken under regular engine loading at sea ..

    #25523

    Antonio micula
    Participant
    Vessel Name: pilotina
    Engines: yanmar 6lya-stp
    Location: europe
    Country: Croatia

    Tony

    It will take some time until i will be able to do a backpressure test.

    Tomorow i will post some photos of exhaust system.

    I hope you dont mind if i ask a few questions

    1.does engine has to be loaded(running a boat) while taking a readings…..all rpm ranges?

    2.if we allready did confirm that boost pressure is OK….is there anything else how backpressure can cause problems (especially black smoke)

    Thank you

    #25520

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    Your EXHAUST TEST was bogus. 6 BAR would be a 0-90 PSI scale–I am sure it didn’t move.. You can BLOW , maybe 2 PSI below your cheeks hurt.

    Exhaust pressure must be measures with a differential pressure gauge in the 0-6O” or 0-100″ of WATER

    28″ of water = 1 PSI ———-Once you exceed 1.5 psi, ( about 40″ of water) things can go south quickly

    Look up Magnelic “mini-gauges” —- Accurate, Cheap & rugged

    Use 1/8″ Silicone vacuum hose to the connections

    Tony

    #25519

    Antonio micula
    Participant
    Vessel Name: pilotina
    Engines: yanmar 6lya-stp
    Location: europe
    Country: Croatia

    1.I have personally installed boost sensor and it is installed on the dedicated place for it next to oil pressure sensor , this means that boost is measured after intercooler

    2. I did measure back pressure , and it was 0 (zero) psi….i did measurement with analog pressure gauge with 6 bar scale and needle wasn’t move at all

    Right now I am at work , but i will ask my friend to take some engine photos and i will post it tomorrow.

    #25518

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    #2 sounds suspect………….The aftercooler needs to be completely taken apart and then cleaned properly to be sure.. Maybe this needs to researched deeper to see what was really done.

    EXACTLY where are you measuring boost? Before the aftercooler or after the aftercooler?

    Have you measured exhaust back pressure? This needs to be done .. Can I see what you have as to a riser or elbow that is connected to the turbo?

    Tony

    #25515

    Antonio micula
    Participant
    Vessel Name: pilotina
    Engines: yanmar 6lya-stp
    Location: europe
    Country: Croatia

    1. yes turbo just came back from overhauling from specialized company , and exhaust is OK

    2. as far as i know , mechanic took intercooler to his workshop and soak it in some liquid….I dont know more details

    3. I have check rpm with special instrument and then compare with yanmar tachometer…yanmar is showing 70 rpm more….so I am deducting 70 rpm from yanmar tachometer

    4. it is 3700 rpm on yanmar tachometer…if I deduct 70 rpm that is 3630 rpm

    5. yes I am measuring boost pressure….at max rpm is over 2 bar(30 psi)….the max scale on the instrument is 2 bar and it is going even more….before turbo overhaul it was 2 bar straight
    At 2700 rpm which i like to run most is 1 bar (14.5 psi)

    #25507

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    1) Your turbo exhaust side is 100% so we eliminated and is most common or when I suspected

    2) Answer Robs ?? about how the aftercooler was serviced–Core removed on the BENCH and cleaned the AIR SIDE 100% “spic & span”

    3) How are you measuring actual RPM’s??

    4) What is you NO LOAD RPM in neutral, engine at operating temp?

    5) Are you measuring boost pressures?

    FIVE ?’s–Need FIVE answers……..

    Tony

Viewing 20 replies - 1 through 20 (of 40 total)

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