In article , F330 GT
writes
Rick,

Sounds like trim tabs would do more for you than changing props. Their is
probably no better way to achieve slower planing speed than good trim tabs. Of
course, that certainly won't be the most economical speed. Most new outboards
are most economical in the 3500 to 4000 rpm range.

Surely you mean most efficient, not most economical. There is no way an
outboard running at 3500rpm gets less gph than one running at 1000rpm.
Equally, there is no way it gets better mpg than one running at 1000rpm.
Only, m/g/h would it be more economical. I can run all day on a river at
1000rpm (6mph) and only use half a tank. Run on a lake at 25-30mph and
3500rpm and I get through a whole tank in a few hours!
--
Nick