The 998 unit uses a Side Imaging (HDSi) transducer. You will have to mount and use this new transducer to get the Side Imaging and Down Imaging sonar. It will also give the 2D sonar but many end up mounting their HDSi transducer were it is less likely to get damaged from hitting something (but still able to give good Si/Di sonar readings) and use a second DualBeam transducer for the 2D sonar but it is usually installed inside-the-hull on fiberglass boats. An AS-Si-DB-Y cable is needed for this. Your Matrix 17 unit uses a DualBeam transducer.