Based on past discussion, I am under the impression that
an outboard will work the most efficient if it is being
run in wide-open-throttle. This means I am looking for
a motor that can satisfy the requirements stated above
when it is being run in wide-open-throttle (instead of
getting a BIG motor and then running it at low speed).

You may want to rethink running wide open at cruising speed.
Reliability will suffer and fuel consumption wont be
significantly better than a moderate sized motor running
at 70-80% of full throttle.

Thanks for the correction. I must have misunderstood other people
advice. OK, I will have to assume that I will be running at 2/3
throttle most of the time instead of at WOT. I am glad that you have
corrected me before I wasted my money on motor that is under powered
and have to be run at WOT all the time.

Jay Chan