Prop sizing?

[balsl6]

I have a 94 johnson 115, i currently run 13 3/4 x 15 prop it has great take off but lacks a little on top end. I tried a 14x17 and it lacks on the low end. Is there a prop in between that I could get in the middle of these 2? It runs a little high on the RPM with the smaller prop and a little low with the bigger (200-300rpm).

It is on a 170 sportfish.

Thanks