AN SMA ACFT IN CRUISE DECLARED AN EMER AND DIVERTED DUE TO ENG PWR DECREASING CAUSED BY A BROKEN EXHAUST PIPE.

Narrative

AN ABRUPT PARTIAL LOSS OF PWR WAS EXPERIENCED; ACCOMPANIED BY ROUGHNESS; A CHANGE IN THE SOUND OF THE ENG; AND THE LOSS OF ABOUT 50 ENG RPM'S. BECAUSE OF MY PARTICULAR LOCATION; AFTER ENGAGING CARB HEAT AND CHKING SWITCH AND VALVE POS I UNHESITANTLY DIALED 7700 INTO MY XPONDER AND DECLARED AN EMER. HAD THE LOSS OF PWR LED TO IMMEDIATE TOTAL ENG FAILURE; I FELT THERE WAS A SLIGHT CHANCE THAT I WOULD NOT HAVE BEEN ABLE TO GLIDE TO AN ARPT; AND I FELT IT IMPORTANT THAT OUR PRECISE WHEREABOUTS BE KNOWN. I TRIED CARB HEAT; A MAGNETO CHK; AND ALTERED MIXTURE SETTINGS; NONE OF WHICH HAD ANY SIGNIFICANT EFFECT UPON THE CONDITION. ALTHOUGH A GLIDE TO THE NEAREST ARPT WAS SOON ASSURED; I ELECTED TO NOT CANCEL THE EMER UNTIL AFTER LNDG BECAUSE I HAD NOT BEEN ABLE TO DIAGNOSE THE PROB INFLT. FINDING MYSELF OVER THE NEAREST ARPT (MARIPOSA) WITH AN ALT LOSS OF ONLY 1500 FT; AND STILL PRODUCING PWR; I ELECTED TO CONTINUE TO MERCED; PROVIDED THAT I COULD ASSURE MYSELF TO BE WITHIN AN EASY GLIDE OF EITHER ARPT BEFORE COMMITTING TO MERCED. THE LNDG AT MERCED WAS UNEVENTFUL. MECHANICAL SUPPORT SVCS WERE NOT AVAILABLE ON THE FIELD. THE FOLLOWING DAY I REMOVED THE ENG COWL AND FOUND THE PROB TO HAVE BEEN NOTHING MORE THAN A BREAK IN A TAILPIPE. IN ORDER TO EXPEDITE THE REPAIR DURING DAYLIGHT HRS; I ELECTED TO REMOVE THE AFFECTED PART MYSELF IN PREPARATION FOR THE MECH'S LATER ARR WITH A REPLACEMENT PART. I FLEW THE ACFT TO ITS HOME BASE (STS) THE FOLLOWING MORNING.