I have a Lowrance 520c GPS/Sonar combo on the bow of my boat. It is matched with the Universal Sonar 2 in my Minn Kota trolling motor. I just upgraded the software in the unit after putting it off for a year or so. After doing so I noticed that there is a "transducer select" module on the graph. It has a drop down box with about 20 different transducer types. Does anyone know, or know where I can find out, which selection matches with my Lowrance 520c?