We'll make this easy for you. Go to this URL first and when you get there click on the agree button:
http://www.garmin.com/products/gpsmap162/agree.html
That will get you into the 162 software page and one of the first things you'll notice is on the right side where it tells you:
Beginning with software version 3.03, tide station data is stored in the same area as MapSource Maps. If you update your software from version 2.61 or earlier, you may lose all tide stations. If this happens, and if you would like to use the tide prediction feature of your GPSMAP 162/168 Sounder, please download and install one of the following:
Recommended MapSource U.S. Tides Software:
If you do not own a MapSource product which contains tides, but you do own another MapSource product, you can download and install the free MapSource U.S. Tides software below. You must already own a MapSource product for this download to work. You can combine tide stations coverage from the Tides product with maps from other MapSource products and upload this to your unit.
Download (4.89 KB) β MapSource U.S. Tides
Restoring Factory Tide Settings:
If MapSource data that does not contain tide points (e.g., U.S. Topo) was already loaded into your unit before you downloaded new unit software 3.03 or above, and you simply want to restore your pre-existing tide data, please download this file below. This will replace the MapSource maps with tide data.
Download (1.28 KB) β Preloaded Tides
Hope this helps.
Thom
"I command thee, O fish of the ocean, rise to my bait"