If 4800 rpm is the WOT you are propped correctly.
You did not say how many folks you normally have on board but a 1800 is not a big boat so just a few bodies on board and if they sit near the stern will impact the performance. I recommend adding smart tabs.
I do not recommend a foil as I think they provide little help and stress the plate on the drive.
Have you tried moving weight (people, cooler, ..)to the bow to see if that helps?
1997 2400 SCR
5.7 Vortec / Bravo 2