"Matt Koch" wrote in
:

For what it's worth, I also have a yanmar single cylinder engine in my
boat, a YSE8.

At idle it is also very rouogh and loud, I also get a little oil
coming out fo rthe wxhasut when its cold and I have the black transom
syndrome. I have had the injector tested and adjusted but still get
the black moustache.


Matt, does it black smoke when you run the throttle up to full? Many small
boat diesels are way overloaded with too much prop. This will manifest
itself worst when you shove the throttle up to full and let it run at full
throttle for a few minutes. Overloaded diesels will not burn all the fuel
oil being poured into them because their overloaded RPM won't come up to
suck in enough air. The results is carbon pouring out the exhaust,
especially at full throttle....

Signs of overload are when it won't come up PAST the instruction manual's
full speed RPM, black smoke gets worse the longer you run it wide open and
it just sounds awful. You can see the same overload when a trucker has his
foot against the firewall in too high a gear with black smoke pouring out
his stack onto the pretty cars.....

The carbon black you see on your hull may be an overloaded diesel at
partial throttle, where the carbon produced isn't bad enough to see.
Running it at full throttle against the stop shouldn't produce excessive
smoke and you should be able to get the RPM up past full specs without
waiting a week.

I've never figured out why boaters are SO enthralled with diesels lugging
along at 1200 RPM that are made for 3600-4000 RPM by the Japanese geniuses.

Larry W4CSC