MOONEY PLT ATTEMPTED VFR FLT WITH GND OBSCURED BY CLOUDS. A NAV FAILURE CONTRIBUTED TO DISORIENTATION AND UNAUTH PENETRATION OF CLASS B AIRSPACE.

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I WAS FLYING A MOONEY FROM MLB TO SRQ. DUE TO EVENTS ON THE GND THE FLT WAS DELAYED FOR ABOUT AN HR. WE DECIDED TO FLY VFR IN THE HOPES OF SAVING TIME AND ENRTE TO SRQ. SHORTLY AFTER TKOF; WE EXPERIENCED PROBS WITH THE ELECTRICAL SYS AND LOST THE #1 NAV. DUE TO INCREASING TSTMS; I DECIDED TO CLB TO 8500 FT TO FLY OVER THE WX. BY THE TIME I CALLED ORLANDO APCH; I WAS AT 6500 FT AND BY THE TIME RADAR CONTACT HAD BEEN ESTABLISHED; I REALIZED I HAD ENTERED THE ORLANDO CLASS B WITHOUT BEING CLRED. THE CTLR ALSO POINTED THIS OUT. TFC ON HIS FREQ WAS LIGHT AND HE WAS HELPFUL TO RESOLVE THE SIT. A MIN LATER I DECIDED TO DSND TO 2500 FT AND GO UNDER THE WX. I WAS NEVER IN IMC; BUT AT TIMES; REF WITH THE GND WAS DIFFICULT AND IT MADE PILOTAGE DIFFICULT. AFTER DSNDING TO 2500 FT; I REMAINED ON FLT FOLLOWING UNTIL SRQ WITHOUT FURTHER EVENT. LOOKING BACK; I SHOULD HAVE CONTACTED ORLANDO APCH IMMEDIATELY AFTER TKOF OR JUST TAKEN THE TIME TO FILE IFR. I WAS ALSO NOT USED TO FLYING ABOVE 3000 FT WITHOUT AN IFR FLT PLAN.