I HAVE AN 1979 115 HP EVINRUDE, ALWAYS TAKE GOOD CARE OF IT AND MAINT. THE OTHER DAY I WAS GOING ACROSS THE LAKE START TO TAKE OFF REAL GOOD AN PLAN OUT, THEN THE ENGINE REVED UP REEL HIGH I SHUT IT DOWN AND THE ENGINE WAS STILL RUNNING, IN LOW IDLE THE BOAT WOULD STILL MOVE BUT WHEN I WOULD TRY TO TAKE OFF AGAIN IT WOULD REV THE ENGINE UP HIGH, WHAT COULD BE THE PROBLE, I WISH I HAD THE MODEL NUMBER I HAVE LOOKED BUT IT IS SO OLD IT MAY HAVE FELL OFF OR WORE IT OFF. THANKS ANY HELP WOULD BE APPRECIATED