It get mostly positive reviews on Amazon, but no one talked about using one on a cat. I like the fact that is comes with coastal charts and floats/is waterproof. One drawback is that the screen is polarized and one person said that you can't see it with polarized glasses.

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Mike Brady
Sugar Land, TX
Sailing off Magnolia Beach in Lavaca Bay TX
http://358degrees.blogspot.com/
P16 "Pooh Cat"
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I have the older version, the 76Cx, same unit with a few less functions. You have to be careful if you buy one, there are differences between the straight 78, 78s, 78sc, & quite a bit on the price.
The main difference between mine & the newer version,(78xx) are as follows. Most expensive 78 has:
*electronic compass, it works like a regular compass, you don't have to be moving.
* ability to import maps from almost anything. ie, you can look at a Parks Canada,(or Ntnl Parks Service in
the US), university Campus etc, online, & import it into your unit.
* floats (not really any advantage, read on)
* turn by turn navigation
I have never used polarized sunglasses with mine, but regular sunnies are fine. With the "data" screen up, & set to "large" font, you can easily read the 3 parameters,(can be changed to whatever 3 you prefer), with the unit strapped to the mast, from any where, including trapped out. The display is very easy to read in bright sunlight.
Battery life is as advertised, unless you use the backlight,(only needed at night) I am only on my second set of 2 AA cells. I bought a brick (24) Duracells from Canadian Tire for $10, it looks like that will last years.
Floating is useful if you drop it off your dock. If you drop it off the Cat under way, kiss it goodbye. They do float, but barely, & being dark coloured they are impossible to see & find if they go overboard at any speed, unless you have a 6" bright float attached to the lanyard. I keep mine zipped in the pocket, or tethered to the boat.
They are "waterproof",in this case IPX7, which is defined as 1 meter for 30 minutes. This at least gives you an objective test that they have to meet, & I have dropped mine off the dock. It does NOT mean no water ever gets in. I have found drops inside the battery case, & often inside the cover for the mini USB port. If I am only using it to record a journey, I stick it inside a bag, then put it in the tramp pocket. The bag does not have to be a dry bag, even a ziplock or bread bag tied shut will suffice. I have rubber banded it to the mast & subject it to hours of spray, waves & downright immersion with no ill effects, so far. Disclaimer- I also paid $23 for the 3 year no hassle West Marine replacement warranty.
After a pound em sail, I dry it off, & open all the ports once I'm indoors to dry out any moisture that did get in. I am also fresh water only.
Very basic use can be done even if you are brain dead, for anything else there is a learning curve. They are not as simple as the Garmin units designed for autos, you will need to play with it to get the data fields set up for your situation, & learn how to input waypoints & build routes. You will NOT be able to drive a Cat in 20 kts & navigate from the map using the small screen. Best is to have the course pointer up, you can easily see where you should be going, but as with all GPS, they are not great for strategic planning, you don't have a big enough picture. My lake is big enough that we can't see the far shore, the unit is useful to keep on the right heading, as in reference a cloud, drive for 10 minutes, check again, correct, drive on. If the wind is low enough to allow you to just sit on the hull, fill 'ur boots, you can play around & navigate with them. As said, if you are out on the wire, you won't have time to hold it & go through screens looking for navaids or follow the map. They are useful if you are trying to miss that 1 rock where you normally sail. The map can be zoomed, & you will be able to see your position relative to the object you want to avoid. Or input the reef as a waypoint, then "GO TO", the bearing pointer, in conjunction with a couple of data fields on the same screen should keep you clear.
The G2 Marine maps come on a micro SD chip, & they are not locked to the unit, as most Garmin databases are. You can put the chip in any compatible chart plotter, even your Nuvi, (though it won't show all the marine data in the cheapo car GPS unit). The cheapest I'd ever seen the Canadian Great Lakes G2 chip was $130. I got the 76Cx with the chip on clearance at West Marine for $130, & I wanted the chip for power boating, so I figure I got the unit free.
The software that comes with it (MapSource), I think retails for $75, but it is garbage. It does allow you to build a route from another Garmin Map & import it to the device, but how it depicts routes you've sailed is pretty crappy. However there is a button,(hidden in "view") "display in Google Earth", that gives you one click access to see your route on a real map. Once you understand how to really use Google Earth, you are golden.
Garmin sells individual "City" maps for $10, & a city is actually quite a large area, in the case of Toronto, it goes from the US border north to Lake Simcoe, over 100 miles. Many people would never use this as they have a Nuvi, TomTom etc for N America. I use it for walking in cities around the globe I get stuck in for work. That gives me detailed navigation, & 18 hour battery life. If you've ever walked in Venice you will know that paper maps are sh**t!

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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It was incorrect to state that the older 76Cx does not float. It is the same case & controls as the 78. I set mine in the lake beside the dock today, it does indeed float. They float in a "flat" position, but if it happens to be backside up, that side is very dark & extremely hard to see.

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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The only real advantage to being offshore and having a device that floats is when you are separated from the boat and in the water. Nice to have the GPS or radio stay afloat if they come unclipped from your vest/harness.

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Sheet In!
Bob
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Prindle 18-2 #244 "Wakizashi"
Prindle 16 #3690 "Pegasus" Sold (sigh)
AZ Multihull Fleet 42 member
(Way) Past Commodore of Prindle Fleet 14
Arizona, USA
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