I agree....balance of the prop and make sure that it is on the shaft straight and tight.......make sure that the hole in the prop is centered......if the hole in the prop needed to be stepped up bigger did you drill it or ream it by hand...if you drilled, the hole is probably off......
Make sure the engine mount bolts are tight and that the mounting feet are all the way down on the mount....if you can't find anything get a new prop