Similar thing happened to me, my laptop used to overheat playing FM13 but was fine with FM12.
Only thing I can suggest is turning off 3D, playing with a smaller data base and/or selecting fewer leagues. I was only able to select 4 without it going too slow and overheating, and the rest are view only.
Downloaded skins also seem to slow my game down, so I play with the original dark skin and only use club/competition logos.
I heard changing the rendering mode from 'GPU assisted' to 'Software' also speeds the game up slightly.