I got the boat in the water today. It was running great until I shut it down for a few minute to go under a bridge by paddle with the stern drive up. I put the drive back down to the trim up position (shallow waters) then started the engine and when I shifted into drive I got a loud clunking noise. It reminded me of the sound of a bad u joint on a car. Is that what I'm looking at and how hard is it to change them?