overheating power

Hey guys, im new to this to this site. but i need some help; my amp is overheating, blowing fuses, and this all happens within 20 mins of playing. plus the amp sounds like its playing at half power. this started about 2 days ago. is my amp on its way out or is it my ground? my ground is secured...

I have a MB Quart OA800.4 wired to 2- 6x9s (Kenwood) & 2-6.5 Kicker wired correctly with 12 ga speaker wire. Power wire is 4ga & have had the amp in numerous locations, one being on the outside of my sub box & it's overheating even without really pushing it. The amp now is in a...