PLT INFORMED PROHIBITED AREA EXPANDED; CHART DOES NOT SHOW CHANGE. NO NOTAM.

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I WAS FLYING IN THE VICINITY OF KENNEBUNKPORT; ME. FLT WAS VFR. THE CURRENT CHART; NEW YORK SECTIONAL DATED 5/91; SHOWS PROHIBITED AREA P67 AS A 1 MI DIAMETER CIRCLE AND A 1000 FT TOP. I AVOIDED THE AREA ENTIRELY FLYING WELL TO THE W OF THE AREA AND USING THE GND OBJECTS AS REF TO STAY OUTSIDE THE PROHIBITED AREA. ALT WAS 1500 FT; WELL ABOVE THE PUBLISHED MIN ALT. I TRIED TO REACH PORTLAND APCH; BUT DUE TO OTHER VOICE TFC IT WAS SOME TIME BEFORE I COULD CONTACT THE CTLR. UPON CONTACTING THE CTLR; IDENTING MY ACFT AND ASKING FOR FLT FOLLOWING; I WAS TOLD THAT I WAS IN THE PROHIBITED AREA AND TO FLY DIRECTLY N. I ACKNOWLEDGED AND COMPLIED. I TOLD PORTLAND APCH THAT MY CHART SHOWED ME WELL CLR. I WAS TOLD THAT THE PROHIBITED AREA WAS 4 MI IN DIAMETER; AND NOT AS SHOWN ON THE CHART. SHORTLY THEREAFTER APCH CTL TOLD ANOTHER PLANE ON THE FREQ THAT THEY WERE IN THE PROHIBITED AREA. I LEARNED LATER FROM THE FBO WHERE I VISITED THAT THIS IS A COMMON PROBLEM AND MANY VISITING PLTS ARE VIOLATING THE PROHIBITED AREA BECAUSE OF THE IMPROPER LIMITS SHOWN ON THE CHART. IMPROPER CHARTS LEAD TO POSSIBLE CONFLICTS AND ACCIDENTS AS WELL AS UNNECESSARY PROBLEMS FOR ATC. I STRONGLY SUGGEST THAT PUBLISHED CHARTS USED FOR NAV BE RIGIDLY INSPECTED FOR ACCURACY BEFORE PUBLICATION. A PLT WITH A 'DISPUTE' WITH ATC IS A DISTR PLT AND NOT CONCENTRATING ON SAFE FLYING. WE DON'T NEED DISTR PLTS IN CONGESTED AIRSPACE.