straight from mercurys website
4800-5200 rpm

https://www.mercurymarine.com/en/ca/...specifications

you running the oem cat equipted motor or the repower 300 MPI like this https://www.mercurymarine.com/en/us/...a-sterndrives/

neither.
my motor is a mercruiser new motor, not a reman plus alpha series.
its a seacore mpi infront of a bravo drive

does it have cats?

no cats

cat motors like the one you linked, turn to 5200, cats hurt the power so they turned them harder to make the lost power up. Non cat motors turn to 5000 before they start pulling power.

I know mine said it could go to 5200, but it sure started laying down above 4900. Propped it to run at 4700 and it went about 9 mph quicker than it did at 5150.

The outboard manufacturers will advise that if the motor isn't propped to reach max rpm, the engine is not running properly, and damage possible.

Over propped, lower rpm.........engine is working too hard and strains.
Under propped, higher than recommended WOT rpm, and spinning too fast.

Some of you may disagree, but that's the general standard .