sure sound like a U joint. Be careful with leaving it in the water sometimes it can take out the bellows as well. Take a look around the inside where the shaft comes through the gimbal bearing and make sure no water is coming in. Another big cause of that also comes from running the boat with the drives trimmed up to high. If you trim way up because of shallow water or accidently fire the boat up while its still in trailer position that will tear them up pretty good as well.