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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
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