How much play is a prop suppose to have

[boater1234]

I have a 15hp merc 2stroke,it is a 2001 model and i was wondering is there suppose to be a little play when you put the prop on the shaft.My prop does not have to much play but if you take your hand and make the prop firm,then try to move it from front to back it has like a really,really small amount of play in it.Is this normal?Also what is the shaft made of?Thanks for any info.