WHILE ATTEMPTING TO UNDERSTAND THE MSG FUNCTION OF HIS ADVANCED NAV SYSTEM; A PA28 PLT LOST SITUATIONAL AWARENESS AND CLBED INTO BOS CLASS B AIRSPACE.

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VFR FLT PLAN. OPENED FLT PLAN AND CONTACTED BOS FOR VFR ADVISORIES. INITIAL CRUISING ALT 2600 FT MSL. AFTER PASSING OWD; TURNED ON COURSE FOR ACK. I WAS USING KLN-89B FOR FIRST TIME AS PIC (WITHOUT INSTRUCTOR). I HAD AN INTRODUCTORY FLT WITH AN INSTRUCTOR ONE WEEK PRIOR AND I FELT I KNOW HOW TO USE THE DIRECT FUNCTION; WHICH WAS THE ONLY GPS FUNCTION I WAS GOING TO RELY UPON. IT WAS A REPLACEMENT FOR THE RNAV SYSTEM I HAD BEEN USING ON OLDER ARROWS. MY PLAN WAS TO ENTER DIRECT TO OWD AND; UPON PASSING OWD; ENTER DIRECT TO ACK. SHORTLY AFTER DEPARTURE; I BEGAN RECEIVING AIRSPACE MESSAGES. I WAS HAVING TROUBLE FIGURING OUT HOW THE MESSAGE FUNCTION WORKED; AND HOW TO MAKE THE MESSAGES GO AWAY WITHOUT LOSING MY DIRECT TO SETTING. I RECEIVED REPEATED AIRSPACE MESSAGES WHILE FLYING AT 2600 FT; EVEN THOUGH I WAS STILL BELOW AND CLR OF BOS CLASS B AIRSPACE. I BECAME CONFUSED ABOUT WHICH KEYS; M; ENT; CLR TO USE TO MAKE THE MESSAGES GO AWAY. IF I HIT CLR; IT SEEMED TO ENTER BOS INTO THE DIRECT TO FUNCTION. IF I HIT M; IT DIDN'T SEEM TO DO ANYTHING; I STILL GOT THE MESSAGES. I BELIEVE I BECAME DISTRACTED BY THIS AND ALSO STARTED DISCOUNTING THE AIRSPACE MESSAGES. BECAUSE I WAS USING THE GPS; I WAS NOT FOLLOWING MY TRACK CLOSELY ON MY SECTIONAL CHART. AFTER PASSING SSW OF THE CLOSED WEYMOUTH NAVAL AIRSTATION; MY POSITION WAS CLOSE TO THE BOTTOM EDGE OF THE SECTIONAL AND I FLIPPED IT OVER TO LOOK AT MY ANTICIPATED COURSE. AT THAT POINT; I LOST SITUATIONAL AWARENESS AND MISTAKENLY BELIEVED I WAS OUT FROM UNDER THE BOS CLASS B AIRSPACE AND INITIATED A CLB TO 3500 FT MSL. AT AROUND 3300 FT MSL; THE CTLR ASKED ME WHAT I WAS DOING; TOLD ME TO ASK FOR CLRNC BEFORE CLBING INTO THE CLASS B AIRSPACE AND THEN CLRED ME INTO THE CLASS B AIRSPACE AT OR BELOW 3500 FT MSL.