I replaced my Lowrance 480, same size as yours, with a Hbird 797 and it fit in the existing hole perfectly. A little harder was fishing the wires, slightly tight fit but an electricians fish tape made it easier. Hardest part was changing out the GPS reciever on the back right corner. I took off the chrome vent and reached through there to access the screws below, thats right its screwed from the bottom. Of all the things I love about my Pantera IV, it seems like somebody had a brain fart when they came up with that design. I think its a Lowrance mounting design, not a BassCat thing, but it will wear on your patience. Overall a 3 out of 5 on the difficulty scale. Would have easily been a 1.5 if not for the receiver screws, my short fat arms and large belly!!!!!!