fresh water pump rebuild mercrusier help

[rlsteel]

I am replacing the impeller in my 1995 Rinker 454 mercrusier brovo 1.I bought the sierra part # 18-3150 kit and every think makes sense except the smaller of the two rubber gaskets-o-rings.Where does this go? It kinda looks like the one on the main body of the shaft-fuel pump mount but I will be darned if i can get the old one out, What am I missing here. thanks Robert