Newbie with 25Hp prop question

Hi, I just joined the forum with the hope that someone can help me ID the prop thats on my '92 Merc 25. Its an aluminum prop that appears to have been reworked. The only identifying marks on it are a few numbers stamped on the side. The #s are 1 712B. I put a space between the 1 and the 712 because that is how they are on the prop.
I measured the distance from the center of the prop shaft to the underside of the cavitation plate and its slightly over 5". I did this so I'll know what the max diameter prop is that will fit.
I'm trying to determine the diameter and pitch of the prop so I have a starting point with figuring out what prop I should buy for my 10' FeatherCraft that is running at 4800 RPM at WOT.
Am I correct in thinking that max rpm should be closer to 5500?
Thanks alot, in advance, for any help.
Wet Willie

Most 25 Hp have several diamter and pitchs for diffrent use. They range form 10 dia 15 pitch to 10 3/8 X11. I use a 10 diam. by 13 pitch on all my 25hp Mercs with best performace.I try to keep my wot alittle below the top wot . 1 inch of pitch will lower or increse the RPM by 500. you can go to most prop manufacture web sites and they sometimes have a section that describes what I've stated.