Hi Sebastian,
Someone else will have to help you w/ re. the black smoke/oil, but if
you're boat has fresh water colling, pull and open up the heat
exchanger. Frequently, a scale builds up in the raw water side that
over time, both reduces the flow of raw water and acts as an insulator,
inhibiting the heat transfer. Put it in a bucket and fill the heat
exchanger with straight Lime Away (available in the cleaning section of
most grocery stores) or similar product. When the foaming/fizzing
stops, flush with water and you've likely fixed the problem for a buck
(the stuff is really cheap).

If you've got raw water cooling, this same scale can build up blocking
the passages in the engine block. This is a bit more involved to clear
out. Some people use a mild or very mild acid solution (diluted muratic
or acetic), but I suspect the same product would work here too.

Good luck - Dan Best

Sebastian wrote:
Our 1986 Catalina 27 with Universal 18 diesel tends to run hot
(although not immediately, takes many hours), has low RPMs (always,
although it ranges between 1750 and 2000 at full throttle), and always
give off some black smoke. Additionally, it appears that there may be
a tiny bit of black oil leaking behind the transon of the boat, but
not a lot. Finally, we get a maximum speed of 4 1/2 or 5 knots in
still water, which seems to be too little...

I am quite new to diesels, so know very little. Can someone recommend
some easy things to check/fix. I've heard black smoke means injectors,
but could that also cause the low RPMs?

Thanks!

--
Dan Best - (707) 431-1662, Healdsburg, CA 95448
B-2/75 1977-1979
Tayana 37 #192, "Tricia Jean"
http://rangerbest.home.comcast.net/TriciaJean.JPG