I run a 2d unit on my US2 rigging. Like crappie limits I'm just looking for fish depth to adjust hooks. I runn a stick steer so I have a 998 at my right knee so I can watch both at same time. I fish with a guy who has 998 mounted on his V2 and I can assure you you won't like dealing with the cable and lots of distortion in DI/SI with motor moving. I would just buy the best color 2d and run it on US2. Think if I was going to replace mine right now it would be the Garmin 550C. If set on SI/DI get one of these
http://www.podunkideas.com/l-model.html
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Charlie Weaver USN/ENC 1965-1979