I'm running a 21 RFL w/ a 140 tohatsu, but the prop doesn't say what pitch it is or anything??? Probably going to take it to Baumann soon and get it re-cupped.
I would try a 17-19 p. Call Roys Propellor or Coastal propellor I think they changed the name to in Corpus. He should be able to fill you with info on that boat.