After reading all of this, my impression is that the 2GM likes to be
run at high RPM for a long time. Is this correct? On most of my
"cruise", I have run the engine almost all out because I have rarely
had wind or it was always dead on the nose.

MOST diesels will optimize or get maximum service life if run at 75% of
max. rpm.

In article .com,
wrote:

After reading all of this, my impression is that the 2GM likes to be
run at high RPM for a long time. Is this correct? On most of my
"cruise", I have run the engine almost all out because I have rarely
had wind or it was always dead on the nose.

Rich Hampel wrote in
:

MOST diesels will optimize or get maximum service life if run at 75% of
max. rpm.


I used to believe this, too, until a friend sold his Hatteras 56 with twin
Detroit Diesel 8V92TA twin turbocharged firetruck engines in it. He
thought the Hat56 was a trawler, rarely ever running the beasts above
idle/trawler speeds until I came along and one day opened the throttles
full to "blow the soot out" of the wet pipes....leaving a trail of soot
visible from the Space Station if it were passing overhead.

His wife was impressed that it would plane like a runabout. Dan was
impressed when he started gasping for breath after looking at the flow
meters...hee hee.

These two-stroke diesels were taken apart by General Diesel and inspected
after hundreds of hours of this low-speed "abuse", paid for by the buyer
when he sold it. Both engines were in fine condition and GD replaced ONE
injector spring they found a little weak since 1981! Running at 10-15%
power in "trawler mode" didn't seem to have any detrimental effect on them,
at all.....

What a great ride she was after I fixed the Naiad hydraulic stabilizer
control system that never worked. Even in the swells, she rode as flat as
a table while going up and down the swells.

I miss her.....so does Dan's credit card companies when I insisted we "fill
'er up" instead of leaving her empty like he did so the water could collect
in the fuel tankage....(c;

In article .com,
wrote:

After reading all of this, my impression is that the 2GM likes to be
run at high RPM for a long time. Is this correct? On most of my
"cruise", I have run the engine almost all out because I have rarely
had wind or it was always dead on the nose.

It prefers neither full power nor idle. I've found that ours runs best
between 1800 and 2800. We cruise at about 2500 (70% of revs, 50% power)
for 5.5 knots and nearly 30 mpg. We're propped for 3400 max, and it WILL
overheat at that output in just under an hour, as they predicted. Under
about 2000, our mileage falls, so not all the energy is being extracted,
which translates into soot, I suspect. If you're propped differently,
your numbers will differ, of course.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/