I HAVE A 1989 25 HP. IT WAS RUNNING GOOD, THEN IT APPEARED TO BE RUNNING ON ONE CYLINDER. I CHECKED THE SPARK PLUGS, IT HAS GOOD COMPRESSION, AND GOOD SPARK THROUGH THE PLUGS WITH THEM REMOVED. COULD THIS BE THE SWITCH BOX,(POWER PACK) GOING BAD EVEN THOUGH I HAVE GOOD SPARK WITH ENGINE NOT RUNNING? I APPRECIATE ALL THE HELP I CAN GET.