T&T: Ask the question a different way. was: Running higher HP engines at low speeds.

[Faure, Marin]

>Is there anyone on this list who has personally had an engine fail that
was attributed to extended 'low speed' running?

I will be surprised if anyone posts that their engine failed-- quit---
due to slow running.  But it would be interesting to know if someone's
higher-performance engine has begun losing performance, became harder to
start, smoked more, etc. after hundreds-- or thousands--- of hours of
low speed running, or more significantly, low temperature running.
Evidence like this could support the "it's bad for the engine" opinion,
particularly if the engine was then overhauled and problems like glazed
cylinder walls, excessive soot or buildup in the turbocharger impeller,
etc. were found..

But it would still be hard to prove that low-speed running was the
cause, even more so because it's probable the boat changed hands one or
more times prior to the engine needing work and who knows how the
previous owner(s) ran it?  Plus the "run the fast boat slow" idea is
pretty new, tied as it is to the relatively recent skyrocketing of fuel
prices.  So I don't think people have been following the practice long
enough for problems to become apparent.

As fuel prices continue to climb this will motivate more owners of
higher-performance boats to run them slower if they don't opt for
selling out and buying a more economical boat altogether. So if over the
next several years we start to see more higher-performance marine
diesels getting tired before their time-- or not-- we may have the
evidence we need to prove or disprove the notion about lower speed
running being bad for higher performance engines.

But right now all we can go on is what the engine manufacturers and
mechanics have learned--- however they learned it-- and what diesel
engine theory says should happen under such-and-such conditions.

______________________________
C. Marin Faure
GB36-403 "La Perouse"
Bellingham, Washington