Welcome New Guy.... I'm a new guy too. with almost the Exact same setup, except my Terrova is a 55, I bought a HB Piranha Max, Small inexpensive portable unit for Ice Fishing, took the Head and Its now a permanent fixture in the bow of my boat, connected it to the transducer in the Terrova, works great. lets me know if fish are under the Bow.
This forum is Awesome , you will be able to find lots of info on the 998,