Propeller size

[19seacraft88]

Hi Folks;
I have a 1988 Seacraft 23cc. I just replaced my old Mercury with a new Evinrude E-tec 200.
I need a feedback on propeller size. I called Evinrude, they told me to call Seacraft. I called Seacraft, they do not have records on prop size going back to 1988.
I bought a prop from Evinrude, a 15"x15", and it seems to be high on RPM, but low on speed. Should I get a 15"x17", or a 15"x19". I run my boat usually with a full tank, and 2-3 fellow fishermen.
Thanx,
Al