I have the 998csi combo, and it does have an optional wire you can purchase that will project the same screen out to a monitor. That is how I have the unit on my boat, the actual unit is mounted on the helm with the cord running up to the bow, and I have a cheap 15′ computer monitor attached to the front of my boat for viewing. I do still have to return to the unit and use it’s controls to change views or recalabrate, but the picture is actually clearer on the bigger screen.
Not sure if your unit offers the ‘external’ video screen, I’d suggest calling hummingbird and asking them about it, that’s how I discovered my unit’s capabilities.