FLC OF A BEECH 1900 OVERSHOT COURSE INTXN TURN AND UNDERSHOT ASSIGNED ALT.

Narrative

WE WERE FLYING ON V106 FROM ENE VOR. THE 242 DEG RADIAL FOR 31 DME TO RAMEY INTXN AND THEN DIRECT LWM VOR DIRECT BOS. I MADE A MISTAKE AND THOUGHT RAMEY WAS AT 35 DME NOT 31 DME. AT 35 DME I PROCEEDED DIRECT LWM VORTAC. BECAUSE OF THE STRONG WINDS FROM THE N; WE WERE BEING BLOWN TO THE S. THE BOSTON CTLR ASKED US IF WE WERE OFF COURSE. MY REPLY WAS 'NO WE ARE PROCEEDING DIRECT LWM VORTAC.' HE INDICATED RAMEY INTXN WAS 8 MI BEHIND US. ALSO BEING TURNED OVER TO THE NEXT CTLR; THE CTLR INDICATED THAT HE OR THE PREVIOUS CTLR HAD GIVEN US 5000 FT. WE CHKED IN AT 6000 FT LEVEL; OUR PREVIOUSLY ASSIGNED; ALT. WE TOLD THE CTLR OUR ALT OF 6000 FT ASSIGNED. HE TOLD US TO STAY AT 6000 FT. DURING THE INTXN 'MISS' THE COPLT WAS OFF ON ANOTHER RADIO DEALING WITH COMPANY. WE DID NOT HAVE A CHART OUT; SINCE WE BOTH FLY THE RTE ON A ROUTINE BASIS; WE WERE BOTH LULLED INTO BELIEVING; THAT RAMEY INTXN WAS AT 35 DME; NOT AT 31 DME. WE DISCUSSED AT LENGTH THAT FOR TRIPS (ROUTES);WE SHALL HAVE A CHART OUT FOR THE INTENDED RTE TO DOUBLE-CHK ROUTES AND DISTANCES; TO AVOID THIS PROB IN THE FUTURE. AS FOR THE ALT PROB; BOTH CAPT AND COPLT WERE ON SAME RADIO; AND HEARD THE 6000 FT ASSIGNED ALT TO THE BEST OF MY KNOWLEDGE WE REPLIED 6000 FT. THERE WERE MANY THINGS HAPPENING IN THE COCKPIT GETTING PREPARED FOR AN APCH (AT NIGHT) TO RWY 33L; AND WE WERE PERFORMING MULTIPLE TASKS; AT THE END OF A LONG DAY. BOTH OF US ARE USING THIS NASA FORM AS A LEARNING EXPERIENCE TO AVOID FUTURE MISTAKES.