Max speed if you are running a 2.3 gear ratio....like '98 the Merc 90 uses, says that with zero slip your max speed would be 35. With the 30 mph you measure your slip would be 14%....a bit high unless you have a lot of weight in that boat or don't have power trim, or don't trim for the best performance.
If you add 1" of pitch for the prop being cupped, which is the norm...but my opinion is that the 1" is MPH related so it may not count as an additional inch of pitch at 30 mph....but if so,
then you max speed would be 37 and your slip moves up to 19%....pretty sloppy.
5000 rpms says you may need some engine work. The max RPMS I'd think wold be on up to 5500 at least.
