1979 70hp Evinrude running rough

[alwayzracin]

I have a 1979 70hp Evinrude wich I put on the boat at the beginning of the year. I replaced the reeds earlier this year. I was running full throttle and backed down to half and it ran rough for about 15 seconds and shut off. It will start back up but is way louder then before and runs horrible. I checked the plugs and they seems fine. Spark is still good. Is there a chance I broke another read. I need help!! its striper season and I cant get anywhere!!