small prop question

[bigeasy1]

This has nothing to do with my Tsunami,but only a question on a prop.I have a 17 ft aluminum boat for fishing small lakes when im not on the 23 Seacraft.
So,anyway its time for a new prop for this small motor(20hp 1986 Johnson).The 10-1/2 x 11 prop that's on it has a series of slots around the inner edge that faces the motor.
I found a replacement OMC prop with the same size and pitch and the same 14 spline shaft,and it fits fine.
The only difference is that it doesn't have the slots,its just a plain edge. Both are actual Omc props and are listed for this older 20 hp motor(1984 to 1997)

Can anyone tell what purpose the slots serve,and do they both function the same?
Thanks all