I recently purchased 2 Humminbird 997c SI units From The Trolling Motor Doctor after researching them and talking to a guide I will be using. I should have them installed soon and will get back to you after I hit Casitas. If you go to the Humminbird website you can get a lot of info as well as see video and pictures of it. I must say it looks awesome and seems to show everything. That is a 180 degree view and 240 ft to the left and right. It is so clear and I do not know precisely how it works but you can even see fish and structure shadows. No more guessing at what your seeing when you can see the individual branches of an under water tree on the sonar. Well that is what the website shows. I have upgraded to the platinum navionics chip for both units and will link them together. All together I spent $4,800.00 but it is for fishing Casitas right? I will let you know more as I use them and get better with them, from what I can tell so far this system is going to be awesome.
Rich