Only 4500 -4800 RPMS- 90 HP Johnson on 20'SF

[Texascoastalfish]

Hey All,
Have had my 76 20'-SF out and about all around Galveston Bay,and West Galveston Bay in 3'+ chop and I've got to say..What a ride!! Put her quartering into oncoming seas and it was high and dry at 18-20 knts.No pounding. The North wind was howling at 20 mph. With a following sea 3+ chop it was even smoother although I kept quartering and close eye on the swells, they were close enough together to not have too much worry on plowing into the backs. My Brother kept exclaiming. Man this boat rides great ! I was smugly thinking. Those boys on the Forum were 100 % correct. Imitated,,,,never duplicated....OK enough romancing..

In the sheltered bay areas wide open GPS showed 30-31 MPH , but only 4800 or so RPM. Is this a prop issue I wonder ? I'm running 3.75" X 15 aluminum, may motor too low. The Motor was propped for a 17' Magnum trihull before I got it.. But 31 MPH is nice at WOT. What would be the recommended procedure to increase RPM to 5200-5400 ? I believe thats the recommended WOT for a 84 90 HP Johnson.
As always thanks in advance and a Merry Christmas and Happy New Year.