I am by no means an expert but I would think that using the "damaged" prop, when you have a working tach, would likely NOT give you an accurate reading on the WOT range. You might consider having a shop look at the prop and repair it, then test it with the new tach and go from there. In other words, I wouldn't want to base my decision on how the prop / engine are preforming when one (the prop) is damaged. Can tell you that my 1900SR3 with the V6 came with a 14x23 3 blade and with light load I reached about 4700 RPM and 52mph GPS. So, it is propped right for high end speed performance. I did buy a 4 bladed 14.25X19 Solas (recommended by my tech) for "power" use (when yanking my football player sized adult sons up on skis) and it does help with hole shot, staying on plane and I lost only a little of top end speed. I do have to watch the RPM though when using the 4 bladed prop with a light load. Hope this helps and good luck.
Same admiral since 1973
New Boat 8/13/11: Chaparral 206SSI with 5.0 VP GXI SX
Prior Boat: 2008 Maxum 1900SR3, 4.3L V6 190HP, Alpha 1 (great boat)
2010 Ford 150 XLT Super Crew 5.4L V-8, tow package
2008 Infiniti G-35