"Bill Daniels" bildan@comcast-dot-net wrote

If you insist on 200HP @ 4500rpm output at cruise, which you would want to
do to justify all that weight, it might not last as long.

Might not. Big words, indeed.

OK, let's say it only lasts a quarter as long, in an airplane. 2,000 hours
is a feat that has been duplicated, time and again, by those who have taken
the time to engineer an installation. They keep running after that,
according to those who have installed them. Some in very punishing, high
power demand planes. Glider towing is one area that has had some examples
performing in probably as punishing of an environment that you could find.

2,000 hours are what many air cooled airplane engines would love to see.
Most do not make it that long, without having valve or jug problems, or
other problems. So my examples are doing as well as yours, with less
problems.

A structural beam can take a great loading, and not care how many times it
is loaded, as long as it does not exceed design limits. The same idea can
be applied to engines, as it relates to major failures. (yes wear will take
place in an engine, but not at exceedingly faster rates) As long as the
engine is not loaded past design limits, they will keep on running. And
they have proven that they can.

Marine engine applications are much the same, in terms of power demands, and
the length of time that they are called on to put out the high power levels.
Nobody batts an eyelash at a V-6 or V-8 running for thousands of hours in a
boat. Why so with an airplane? Because not that many have tried, and the
commercial manufacturers don't find financial incentive to try. That leaves
it to experimentals.

Boats run at 4500 RPM for hours on end. They don't blow up. Just because a
car does not demand as high power output does not mean that they could not
do so. They can and will. Those who have well engineered airplane
installations have proven that fact. It is only not considered as fact by
those who do not WANT to accept it as fact.
--
Jim in NC