Loose prop?

Joined
May 16, 2012
Location
Bloomington, MN.
#1
I just got a brand new prop for my Mercury outboard and when I initially installed it I tightened it down pretty good. First hole shot wasn't that great but I could get 1 or 2 more mph than I did before. As the night of testing went on the hole shot got better and better and it felt like it could have gone faster than before but it was getting too late to top out. Anyway I got the boat back on the trailer and I moved the prop to see if it was still tight and it was loose but the nut was still on tight. I have heard it is ok to have some play in the prop but I wouldn't know because I am not an expert.

I took a short video of it too see if this is normal or if my prop isn't on right? Is this bad or good?
http://www.youtube.com/watch?v=yknm7IAUtw0&feature=youtu.be