AN IMPROPERLY SET ELEVATOR TRIM LEADS TO AN ABORTED TKOF AND A RWY EXCURSION.

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AS PART OF NORMAL PRETKOF CHKLIST; PERFORMED TESTS OF ELECTRIC ELEVATOR TRIM; FLT DIRECTOR AND AUTOPLT; THEN MANUALLY RESET ELEVATOR TRIM TO TKOF SETTING OF 6 DEGS UP (BUT INCORRECTLY SET IT FOR 6 DEGS DOWN). FLT CTLS MOVED FREELY AND NORMALLY. RECEIVED SQUAWK CODE FOR FLT FOLLOWING FROM POC TWR AND RECEIVED TKOF CLRNC. DURING TKOF RUN; NOSE DID NOT LIGHTEN WITH SPD. AT 70 KT ROTATION SPD; NORMAL BACK PRESSURE DID NOT RAISE THE NOSE. AT 80 AND 85 KTS; NORMAL BACK PRESSURE DID NOT GENERATE LIFTOFF. WITH 2/3 OF RWY GONE; I CLOSED THROTTLE AND BRAKED HEAVILY. I AVOIDED LIGHTS AT THE END OF THE RWY AND CAME TO A STOP ABOUT 100 FT PAST THE RWY END. THERE WAS NO DAMAGE TO PAX; AIRPLANE OR ARPT; AS CONFIRMED BY A WALKAROUND AND BY ARPT MGMNT. DEBRIEF: 1) I SET THE PITCH TRIM INCORRECTLY. FROM NOW ON; I NEED TO READ THE VISUAL INDICATOR BOTH FOR THE ALPHA NUMERICS AND FOR THE GREEN STRIPE NEXT TO THE ALPHA NUMERICS WHICH INDICATES ACCEPTABLE TKOF SETTINGS. 2) CONTRIBUTING TO MY PREFLT CONFUSION; I WAS ENTHUSIASTIC ABOUT TESTING ELECTRIC TRIM AND AUTOPLT; RESULTING IN A TRIM SETTING WAY OUT OF THE ORDINARY IN A 'DOWN' CONFIGN. FUTURE PREFLT TESTS CAN BE CONDUCTED SO TRIM IS LEFT NEAR ITS FINAL DESIRED SETTING. 3) I HAD A R SEAT PAX (A VERY EXPERIENCED EX NAVAL AVIATOR). I WAS PROBABLY BRIEFING HIM ON THE CHKLIST WHEN I SHOULD HAVE BEEN FOCUSING ON THE CHKLIST. I USUALLY FLY SOLO. 4) I AM A LOW TIME PLT. I WAS INDECISIVE ABOUT ABORTING THE TKOF; EVEN THOUGH I HAD A GOOD 5 SECONDS WORTH OF CLUES THAT IT 'DIDN'T FEEL RIGHT.' WHEN IN DOUBT; ABORT RIGHT AWAY. A GOOD LESSON. 5) I AM A NEW OWNER OF A HIGH PERFORMANCE PLANE THAT IS NEW TO ME. FEW PROCS ARE AUTOMATIC OR INGRAINED. I WILL CONTINUE MY ROUTINE OF 3-5 HRS OF DUAL INSTRUCTION EVERY 60-90 DAYS COMPLEMENTING MY TARGET OF 12-15 PIC HRS/MONTH. EMER DRILLS ARE AT THE TOP OF THE PRIORITY LIST. FLT SAFETY; OR BONANZA PLT PROFICIENCY PROGRAM RECURRENT WILL BE SCHEDULED. 6) BECAUSE I THOUGHT I COULD EXTRICATE MYSELF FROM THE ABORTED TKOF BY TAXIING OFF THE GRASS TO A PARALLEL TXWY; I LEFT PWR AND ELECTRICAL ON. A DIFFERENT CHOICE WOULD HAVE BEEN TO SHUT OFF FUEL; CUT-OFF MIXTURE; AND SWITCH OFF BATTERY; ALTERNATOR AND MAGNETOS -- SHUT DOWN -- WHILE I WAS STILL BRAKING; SINCE SAFETY WAS NOT ASSURED. I WILL REVIEW THAT CHOICE WITH MY CFI.