I dont know if you have your mind set on it but SI has limited utility on the bow. You may want to save some money and get a non-SI unit. For one thing, I dont think the 2d sonar (which youll most likely using most on the bow) is that great on the 797. Also, the SI works best at about 3 to 5 mph and as strait as you can keep the boat. Thats cruising with the TM. Just a thought in case you havent considered it.