Bad Vibrations - 2005 SX Drive

[KJC]

I am a relatively new VP power plant owner - former 20 year vetern of OMC power plant and Cobra drive unit - I bought a 2005 19' Doral BR last year with 18 hours on the meter with 4.3L Gx-i for power and SX for drive. The issue is that when trimmed completely down and turned hard to port or starboard I am getting some serious vibrations. If I trim up a little bit vibrations will stop. Vibrating continues whether in gear or out of gear. In the past (OMC life) I have always done all my own service and was able to maintain the same set of u-joints for the 20 years...but because of vibration I had the somewhat local dealer winterize boat and asked them to verify correct engine alignment and check the u-joints - they indicated everything was fine and that vibration was normal - this does not do much for my confidence in them....anyway looking for some input if any of you are willing to weigh in!!!