Mike,
I just purchased and am having installed a 1197 SI NVB. I won't even get the boat until somewhere around July 10th (the anticipation is KILLING me...) I have been trying to learn as much as I can about the unit and have found: http://forums.sideimagingsoft.com/ A forum website devoted to all Humminbird units. Their engineers are even on the site. A wealth of knowledge and great insite into the value of upgrades. Check it out...
Rob