PA28 PLT BECOMES DISORIENTED FLYING ABOVE FOG BANK AND BEGINS APCH TO WRONG ARPT. HE DISCOVERS ERROR; AS DID TWR CTLR AT CORRECT ARPT.

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DURING THE NORTHERN CA PWR OUTAGE; MRY CLASS C WAS NOT IN EFFECT. I CALLED MRY TWR FROM SANTA CRUZ AND WAS ADVISED TO CONTINUE AND RPT INBOUND ON THE 45 DEGS AND TO MAKE R TFC FOR RWY 28R. MRY WAS RPTING 20000 FT SCATTERED WITH A FOG BANK N AND W OF THE FIELD. I WAS HEADING IN OVER THE FRINGE OF THE FOG BANK AT 3000 FT (APPROX 1000-1500 FT ABOVE IT). UPON REACHING THE TOWN OF CASTROVILLE; I CALLED MRY TWR AND ADVISED THEM THAT I DID NOT HAVE THE FIELD IN SIGHT YET. I ALSO ASKED THEM HOW FAR FROM THE ARPT THE FOG BANK WAS LOCATED. THEIR RESPONSE WAS UNCLR. I CONTINUED FOR ANOTHER FEW MINS AND NOTICED THE APCH END OF A RWY BELOW ME WITH PART OF THE ARPT UNDER THE OVCST. ASSUMING THIS WAS MRY (AND I COULD ONLY SEE RWY 28L; THE BIGGER OF THE 2); I RPTED THE 'ARPT IN SIGHT AT MY 7 O'CLOCK.' MRY RESPONDED THAT I WAS CLRED TO LAND RWY 28R. AS I TURNED BACK TOWARD THE ARPT; MRY ASKED ME TO CONFIRM THAT I WAS NOT HEADED FOR SNS. I REPLIED BY TELLING THEM I WAS JUST DOING A 180 DEG TO RETURN TO THE ARPT (MRY). ON MY INITIAL DSCNT; THINGS DIDN'T LOOK RIGHT; AND THE FIELD DIDN'T LOOK VFR; SO I REQUESTED THE ILS RWY 10R. I WAS GIVEN VECTORS 270 DEGS AND TOLD TO CLB AND MAINTAIN 2500 FT AND VFR. AFTER LESS THAN 1 MIN; I NOTICED MRY (THE REAL MRY) AT MY 9-10 O'CLOCK. I ASKED TO CANCEL IFR AND WAS GIVEN BACK TO TWR AND WAS CLRED TO LAND.