Smoke increase on Yanmar 440


La Cozzi Vita

La Cozzi Vita

New member
Hello All,

Maybe I am getting more anal, but I feel my Yanmars are smoking a bit more these days. I just had bottom repainted, props balanced, new cutlass bearings, and prop speed and no change. Maybe it was always like this and now I am looking for it more. Could there be something causing an increase? If its just me, has anyone done something to reduce the smoke.

I even notice a light haze behind my boat on calm days. Barely visible, but its my smoke.

2003 Yanmar 440s with 740 hours.
 
I can say my Yanmar's do not smoke at all while cruising. Are you getting 3300 RPM WOT? I had to have my props repitched to add about 100 rpml
 
Nate said:
I can say my Yanmar's do not smoke at all while cruising. Are you getting 3300 RPM WOT? I had to have my props repitched to add about 100 rpml
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I have not done a WOT test in while. I should and report. The boat did get to 3300/3250 on my last test
 
Dirty air filter as AllDoge says
Worn injector, have you had the injectors tested?
As you have a clean bottom and props we can discount additional engine load
Some yanmars were known to produce black smoke when their exhausts got clogged up with soot. I mention this in light of your last comment and the assumption you have been pootling along for some time. Diesels do benefit from being worked hard on occasion. Call it an Italian tune-up if you will, but it works.
 
Air density is down due to higher air temps. Black smoke is a loaded engine. White smoke is unburned fuel. Have you checked your actual fuel burn with normal speed and compared it to previous trips. We had a pair of Detroits on a previous boat and they would show more haze on the horizon as the air temp went up but never affected speed. Our Cummins motors on the 41 pc are not as affected as the older 2 strokes but same situation. If speed or efficiency are down then further checks needed.
 
Evermore said:
Air density is down due to higher air temps. Black smoke is a loaded engine. White smoke is unburned fuel. Have you checked your actual fuel burn with normal speed and compared it to previous trips. We had a pair of Detroits on a previous boat and they would show more haze on the horizon as the air temp went up but never affected speed. Our Cummins motors on the 41 pc are not as affected as the older 2 strokes but same situation. If speed or efficiency are down then further checks needed.
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Like I said I have not done a WOT test, but performance feels the same. Fuel burn is not any different. I just did some long runs and fuel burn was consistent with previous runs of equal distance and speed.
 
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