John,
If you are wanting to use your new 898c Si unit for depth readings at on-plane speeds than I would also include an XP-9-20 inside-the-hull transducer and an AS-Si-DB-Y transducer splitter cable, if you are going to mount it on the jackplate as Trep suggested.
Join this web site and look at the images in the Installation: Transducer photo folder to get more ideas on where to mount the HDSi transducer. There may be a few who added images of how they have mounted them to their Nitro