Your problem may not be engine wear. It could be related to other maintenance issues. How much time is there on the engine? How much fuel have you run thru it? Is your fuel old stock or new stock? How often do you check and maintain the fuel system components? It could be the that the Enya #3 needs replacing? etc. Perhaps you should drop the engine out and disassemble it and have a look inside. If you do need a new piston and liner you can go offshore and get a ringed piston and liner (hard to find here) or buy a stock ABN replacement piston and liner for much less than Tower gets or you can buy
a Performance Specialties true ABC Piston and Liner set for about $15 more than Tower's stock OS parts but the PS parts will last a long long time. You probably should consider replacing both the front and rear bearings as well if you switch out the piston and liner.