mark, you defended well a poster whose handle is "steve". Unfortunately, you
assumed "steve" is rational. if you knew "steve" a bit more from his wild
claims of knowledge, you would snicker at him like the seventh grade kids do.

The claim has been made by a poster on this ng who calls himself "steve"
that
diesel engines as used on commercial fishing boats are often torn down for
a
major overhaul after every trip to sea, about 700+ engine time.

Anyone here have experience with diesel engines in commercial fishing
boats?
do those guys really trust their lives to engines that won't go even a
thousand
hours? Anybody know why they do this?

A rebuild is done when necessary (obviously). I have heard that a 2-stroke
Detroit will last around 2500 to 3000 hrs (according to a specific owner).
Now in this case the owner I was talking to eventually traded from a 6-71 to
a large bore Isuzu marine diesel which he swears had over 4000 hrs on the
clock. Disney world would do a rebuild on their launches (3-53 Detroit's)
every year but then in the late 80's switched to Perkins 4-128(?) because
they felt the service time was twice that of the Detroit's (4k-5khrs). Now
in reference to the poster he may have been talking to somebody that only
had one ship (with a single) and they could not afford to brake down and
loose a load. So the cost of a rebuild would be much less then the lost of
a catch. Most commercial companies collect an oil sample at each change and
monitor the material in the oil. Companies like Blackstone can tell you
more that you would ever want to know about your engine. They can specify
oil change intervals, leaking gaskets, bad injectors, warn cylinder sleeves
and so on. So it is reasonable but I suspect its not the norm...

mark