I just ran my engine on the hard and noticed that the prop shaft was vibrating about an eighth inch behind the stuffing box outside of the boat at around 600 rpm. The shaft was not spinning just vibrating. I had put a slightly heavier folding prop on. The shaft is 1 in and seems undersized to me gut feel. I can pry the shaft left to right about a 3/16 of an inch just behind the stuffing box from the outside. at higher speeds it calms down. this doesn't seem good to me. Thoughts?