Mercruiser Diesel 4.2 300 (CMD) white smoke problems

[kohler.3276]

Hello,

I've some problems with my CMD D4.2L-300 D-TRONIC DIESEL. It produced a lot of white smoke when idle. The smoke disappears completely when I rev it up to 1300 RPM or higher. I have no problems reaching WOT or cruising rpm (approx. 3200 RPM). The boat quickly goes to plane. It doesn't matter if I take a long cruise for 1h, still, the white smoke will appear when idle.

-There is no water in the oil nor is the coolant level dropping.
-I tried with new fresh diesel with no difference.
-New oil and filters.
-New fuel filters.
-Water temp is 70 C in low RPM and reaches 80 C in 3200 RPM.
-Injectors renovated last year (according to the old owner)

Any suggestions to check next? What can possible the problem be?
See videos (change to 1080p)

Thanks in advance!

 

[aerobat]

Its not firing on all cylinders at idle , you can hear it clearly .

Since you can reach normal rpm,s at wot, the engine starts to fire again on all cylinders at higher rpm,s .

One injector is faulty at idle but kicks in at higher rpm,s .

 

[alldodge]

^^Agree
White smoke from a diesel is from unburnt fuel

 

[kohler.3276]

A big thanks for the replies!
This weekend, I will do an injector test.
I will update the thread after that.

 

[kohler.3276]

So, here comes an update on the problem. I did an injector test, where I loosened the injector pipe sleeve nut at the injectors, one cylinder at a time.
For cylinder no 5 the RPM or the sound didn't change. Hence, the injector 5 seems to be bad.
I will first call a diesel firm and see if they can service/renovate it if not, I will buy a new (expensive...) one. I couldn't find a new one from the article number ( BOSCH 0 432 193 513 939 484), however, I found a new Mercruiser with the number Nozzle-Injection 889885 (quite expensive in EU...).

 

[aerobat]

Good you tested it and confirmed the problem with the injector . Depending on how long you have operated the engine in this condition make also an oil change since you might have diesel in the oil . Check if oil level rised .

 

[alldodge]

Don't know if your injectors are electric or mechanical, but the mechanical ones might be able to be rebuilt