MUARRY LAWNMOWER,MUARRY,42515x92a?

I have a muarry lawn mower,engine OHV17.5 engine molde#OHV175 204803A ENDURO 17.5 OVERHEAD VALVE.
when the lawnmower is cold it starts up fine, it will run for 5 mins. it shuts off, and it loses it's spark to the spark plug. I let it cool down for an hour it does the same thing all over again.HELP what could be wrong.