Try searching this web site for other Ranger boats that have that same setback and see where they have installed theirs. Alternately you can post some pictures of the overall transom area of your Ranger along with a few from each side of the transom and setback areas and at least one looking under the hull. All need to be taken from a low height such as where a transducer would be. My guess would that you will either have to mount it next to the motor (if there is room) or up under the setback area (or install a Thru-Hull HDSi transducer under the setback) combined with an XP-9-20 inside-the-hull transducer and an AS-Si-DB-Y cable to connect both transducers to the 898c Si unit.