I have Bravo 1 outdrives. When drives are all the way down, I hear a noise coming from the port side motor. If I raise the trim up slightly, the noise goes away. It is a rumbling grinding sound. Could it be the gimble bearing? Any ideas?

Gimble bearing is the most likely suspect.

My first thought was a u joint going south. Does the noise change when you turn the steering wheel/outdrive side to side? Also if you have an older bravo setup with the grease able gimbal bearing/zerk you can pump some grease in when the noise is happening and see if the noise changes.

+1

Pull the port drive and stick your fingers up into the gimble bearing and rotate it. You'll know if it is bad.