Water pump bolt broke off

The top luckily bolt broke off and I tried to drill it out and got half way threw center of broken bolt and of course the drill bit broke...just want it out their is room I can put a bolt and nut on back of it if I can make a hole..any ideas on how to get it out or just drill threw it ...do I need to drill closest to the sides and work my way around it?? Any help would be appreciated..