Merc Outdrive Clank

[jcupo6]

So I bought my boat on Monday, and the guy ran it for me and everything sounded fine, except for a low whine. I asked around and people told me that it probably just needs the the outdrive oil to be changed, or it could just be the way the drive sounds. Yesterday I replaced the water pump, and change the oil. There was no metal shavings at all, and the oil did not look milky. Today I started the motor, and there was a loud clank/knocking sound coming from the outdrive. I have read that this could be the U Joint, but it didn't sound like this until I replaced the water pump. It almost sounds like the drive is stuck in between gears. Any suggestions.