I agree w/ Chris, it is likely a problem of units. It is easy to change the units in either Google Earth or on the gps 76 so they match. However, to manually input wpt data gathered on GE into the 76 or any other gps unit is torture--even Dick Cheney would agree to that!
The easy way to get data into your gps when planning a trip or sail is to purchase National Geographic TOPO! for Florida, Alabama, & Georgia. $49.95 at REI (they often have sales with 25% off on one item.) The link http://www.rei.com/product/737963
The NG TOPO! software has excellent digital maps. You can lay out a route with wpts, even for a day sail, then upload it to your 76--as they say, a piece of cake. I've been using this software for years to layout routes for multiday trips--it is great. You may be able to do this with your BlueChart g2 software--I don't know. A word of caution so you don't expect too much from TOPO!--you can only upload/download wpts & routes, NOT maps. You can download to NG TOPO! your daily "tracks" that you generate on your gps. Of course, since you have a Garmin, you can also easily download your tracks onto Google Earth, also. That is neat.
I learned something today. I was looking at Garmin's online User Guide for the gpsMAP 76CSx and searched for "tides." It came up with a brief discussion of pulling up tide charts on the 76, if you had Mapsourch BlueChart g2 software!
So, the friend I mentioned above who could pull up tide charts on her 76, must have had the BlueChart g2 installed. The tides were excellent, but I think I will continue to get my tides off the internet rather than lay out $139 for the BlueChart software. Still, I will be interested in seeing your Garmin 76 w BlueCharts.