Had a zx225 a few years ago and quit fishing. Messed around with it enough that I had it going pretty fast. This zx200 is still factory set as far as I know. 23t prop on the 200 SHO. Had it out tonight. Not much in the boat. Me and the wife. Does 5800 rpm and 64 mph. Warm day warm water. Was hoping to see at least 66-67. What would you do first? I could tell it had more in it somehow.

Put that manual JP up one dot more, maybe two. It'll be better tuned for fast smooth waters, light loads. BUT, having the SHO up that high won't work for all types of rough water running necessarily or varying loads, so pick your poison. Or perhaps get a tuned prop and see how it'll do to get those RPMs up a bit higher.