Mercruiser 4.3L 190hp Q4 Vibrations?

[Kalani 938]

I just purchased a 2006 Tahoe Q4 with a 4.3L V6 190hp Mercruiser motor and I'm having some vibrations. I bought it Saturday and put it in the water yesterday and noticed a vibration at the lower rpm range. It would immediately go away if I would throttle down or up. The dealer had to replace a bearing and a joint near the low end before I bought it and it runs much smoother now than it did when I test drove it, but this vibration has got me a bit worried. My prop does have a decent sized ding or chip in it, but I didn't know if that was the problem or not? The chip is about the size of a BB that would be put in a BB gun. Other than the vibration the engine runs great. Lots of power and the tower really helped with my wakeboarding. If anyone has any info it would greatly be appreciated. Has anyone else ever heard of this problem or experienced this? This is my first I/O motor so I'm very new at this style of boating. Any ideas or is this normal for a Tahoe boat with this motor? Thanks in advance for any feedback