That depends on a few different things worm:
The 997’s originally shipped out with a PC-11 power cable that did not have the built-in noise filter in them. These older cable will plug up to and power the 1198 unit but if you are getting some electrical interference in through the power cable you will need to end up installing the newer PC-11 power cable that has the built-in noise filter.
The XHS-9-HDSi-180-T transducers that were originally shipped with the 997 units did not have the additional noise shielding in the housing of the transducer. They will work with the 1198 units but again; if you end up having interference noise on the 1198 unit you will need to install the newer XHS-9-HDSi-180-T transducer.
If it were me I would just use it as is and if I than have to go back and install the newer power cable and transducer than I would.