I have had this noticable when turning and trimming vibration. Got worse when I put a 4 blade SS prop on it. Changed out the U joints this winter, and the old ones didn't look that bad. 1 of the journals, on each was just starting to wear. My gimbal bearing turns smooth as silk, and don't really want to pull it, for the hell of it. Could it still be the culprit? Coupler looked good when I had the motor out. 2000 searay 245 with bravo2