Being honest, the likely response you will get is asking for current rpm, gps speed and propeller pitch currently...but if it helps and you have no data to go on currently...I would hazard a guess at a 23” to start with.
Mom perhaps comparing it to my old U.K. built racing boat...a Ring 18 with a 98’ Merc 200 on her. She would even turn a 25”...but happiest with a 23”. Both laser 2 props.
The only thing is that I know these bass boats are exceptional in performance and easily run close to 70gps with moderate HP like a 200. But usually rely on jack plates to do this.
Anyway...I’m going on too much. Good start would be a 23”, all else being healthy etc etc.
