RE: FX 46: Liner lost its coating
O.S. Max .46 FX engines made after 1998 or so had the new ABL liner plating system. The engines with the ABL system usually will lose plating only if they have been run with too little oil, or grossly overheated. There were difficulties with the .46 FX engine previous to that with the old plating system.
You would have to discuss resolution with your regional O.S. service center.
You will need at least a new piston/cylinder assembly.