It really gets back to your definition of “will it work…”. Parts of the 598’s Compact Side Imaging (CSi) transducer will work with the 688 ci HD DI model unit but the Sensitivity levels will be different and/or the sonar beam will be pointed in a different direction. It’s not a drop in replacement, nor is it officially recommended that you use a CSi transducer on an DI model unit but it can be made to work in some applications.