LOWE SF 214

Engine Serial Number 2b720296
Prop is 8m 0084494

My FIL bought a new Lowe SF 214 has always said he thought it should run faster than it did, few weeks ago was my first day on it and I think he’s correct. Did some research and found on a Mercury Page testing a 115 four stroke engine in the same boat and it reached a top speed of over 30 MPH, this boat is only reaching 20 MPH.

Pontoon starts instantly, sounds perfect, and accelerates very well. Problem is it’s only turning around 5000 RPM’s at WOT. I checked the throttle butterfly and it is reaching WOT.

1) What is a good Prop Recommendation if not the one currently on Boat?
2) What should WOT RPM’s be in this application?