GA SMA UNAUTH PENETFRATION OF AIRSPACE.

Narrative

ERRONEOUS TECHNOLOGY: MODE C SHOWS 100-200' HIGHER THAN ACTUAL IN THE INCIDENT ACFT. CONFIRMED BY ASKING BOEING TWR FOR MODE C READOUT; WHICH WAS 120' ABOVE OUR ACTUAL. BOEING TWR HAD INFORMED ME THAT MY DATA BLOCK CARRIED A VIOLATOR FLAG. ABOUT 10 MINS EARLIER I HAD BEEN ACCELERATING EBND UNDER THE FLOOR OF THE 3000' SECTOR IN PREPARATION FOR A STEEP CLB UPON REACHING THE 345 DEG SHELF UP TO 5000'. I DID NOT CLB ABOVE 2980' UNTIL REACHING A ONE DOT DEFLECTION PAST THE 345 DEG OBS ON THE VOR; WHICH CORRELATED WITH GND REFERENCES BENEATH THE ACFT: WEBSTER POINT LIGHT WAS 1/2 MI BEHIND THE ACFT WHEN I COMMENCED THE CLB. AFTER RETURNING TO THE W (UNDER THE TCA'S 3000' SECTOR; 2 MI N OF THE 1800' SECTOR AS CONFIRMED BY BFI TWR); I ASKED SEA TWR FOR CLRNC THROUGH THE SFC SECTOR OVER THE SEA ARPT. I WAS ASSIGNED 2500'. I RPTED REACHING 2500' AND WAS CAREFUL TO HOLD THAT ALT +/- 10'. I EXPECTED THAT SEA PERSONNEL NOTED THE HIGH ALT READOUT AND DELETED MY VIOLATOR FLAG; BECAUSE BFI PERSONNEL RPTED NO FLAG UPON MY RETURN TO THEIR FREQ. TO AVOID FUTURE SITUATIONS; CHANGE THE FLAGGING PROCS TO MATCH THE ACCEPTABLE LIMITS FOR ALT RPTING EQUIP ERRORS. THERE ARE TIMES WHEN WE SHOULD BE ABLE TO USE OUR NON TCA AIRSPACE WITHIN 300' OF ITS LIMIT W/O SUFFERING FROM TECHNO PARANOIA!