Vibration in Minn Kota Co-Pilot

I have a Minn Kota Co-Pilot trolling motor. I just had the boat out
for the first time this season and was checking everything out. The
tolling motor is one of the items I found a problem with. It vibrates
badly at all speeds. The strange thing is it only does this in the
water. When I pull it out of the water and run the motor it doesn't
vibrate at all. It didn't do this last year. Could the prop be
bent slightly? I looked at it and didn't see any obvious damage. Any
other suggestions.