Like everyone has said. You have a spun hub. If you want to verify that, draw a line on the back of the prop (see red line in picture) then try it again. If the line is no longer straight, the hub is spun. Take it to a prop shop to have a new one pressed in.
Name:  propeller2.png
Views: 433
Size:  80.0 KBName:  propeller2.png
Views: 433
Size:  80.0 KB