Just after takeoff at 10:06 a.m., the report says a rear passenger commented that the left engine was producing more power than the right and indicated there may have been a faulty gauge. The pilot continued, however. About 10:11, airplane control was transferred to the right-seat passenger, at an altitude of about 4,500 feet msl. At 10:14, the rear passenger made a query to the pilot regarding power to the "alternator." The pilot made a comment indicating that was the "problem;" however, did not specify what the "problem" was or what actions were taken to correct it. Audio indicated the right-seat passenger visually acquired the runway and provided directions to the pilot as to where the runway was. About 10:15, the pilot made comments which indicated he had acquired the runway. After the plane aligned with the runway, the airplane continued to descend to 942 feet msl until the CVR audio and GPS data ended at 10:15:23.