The Signet Depthsounder on my 1985 H28.5 has finally died with no hope of revival. I have purchased a Horizon replacement and want to mount it in the Merryman pedistal mount where the old Signet was instead of bulkhead mounting it. However, I can't seem to remove the old unit from the mount even with the rear of the mount open. I don't want to disfigure or break the mount in the process. Help!