Robert, I posted this reply in your other post titled "Pro ET":
I received a call back from Scott Reichow of Mercury Racing Propellers and here is his advice on checking for the newer thicker blades. For the year 2010 props look for serials ending with the letters "LIL" or "LIS" and for the year 2011 props look for the serials ending in "LLS" or "LLL".
Look at the serials on your prop. The last 3 letters as indicated above are the years for 2010 & 2011. Scott at Merc did not give me the ending serials for pre-2010.