... My question is this- can I power the Garmin with the mini USB cable that comes with it connected to the USB power receptacle that I'm mounting on the bars?
You can however, but using a USB cable into the Unit direct does not charge the unit.
Here's my experience. I was using a USB Cigarette adapter paired with a USB cable into the bottom edge USB port on the 765. It would not charge the 765 and I was having frequent drop-outs / reboots when the USB cable shifted in the GPS.
I put up with it for awhile then justed got tired of the problems while on a 43-day trip. I stopped using the GPS.
Of course, after I got back I did some more googling and found this discussion with pictures over in Sport-touring net. Sport-Touring.Net - Garmin Nuvi 765T issues
If the thread link doesn't work, it is in the Gadgets subforum with a thread title, "Garmin Nuvi 765T issues"
As the guy talks and shows in Reply 12, I realized that I should have been using the Garmin Mount/Clip inside the Ram Mount Cradle. I purchased the proper Garmin 12 V charger (Garmin Straight 18 Pin Cigarette Lighter Adapter Model: 010-10747-03) which I'd never had and did not need to cut down the Cradle as he advised.
Though a bit of pain in the a** to get in place, the GPS is charging and not having the re-boot problems with the vibration.
Not the one in Illinois