On March 15, 2008, at 1431 eastern daylight time, a Cessna 402B, N300SH, experienced a landing gear collapse during landing roll at the Fort Lauderdale Executive Airport (KFXE), Fort Lauderdale, Florida. The commercial pilot and three passengers were not injured. The airplane was substantially damaged. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed for the business flight. The airplane was registered to SHO Enterprise Incorporated and operated by Bimini Island Air under the provisions of Title 14 Code of Federal Regulations Part 135. The non-scheduled passenger flight originated from Freeport, Grand Bahamas at 1400. The pilot stated that upon arrival at FXE, he was cleared to land on runway 26. He said that after he put the landing gear handle in the down position, he observed only two down and locked indications for the nose and left main landing gear. He recycled the landing gear handle, but still got only observed a green light for the nose and left main landing gear. He then used the hand crank to extend the landing gear, but again observed only two down and locked green lights for the nose and left main landing gear. At that point, the pilot advised the air traffic controller that he had a "gear unsafe" warning light. Shortly thereafter, he conducted a fly-by, and the controller advised him that the landing gear looked down and locked. During the landing, the right main landing gear collapsed. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that the right main landing gear down lock micro switch was loose and not fully closed. The FAA inspector also reviewed the operator's maintenance records and interviewed the operator's maintenance personnel. The review and interviews revealed that several days prior to the accident, an adjustment was made to the right "side brace lock link" by the operator's maintenance personnel. The adjustment was accomplished by lengthening the adjustment screw one-half turn. The adjustment that was made to the right side brace lock link was beyond the manufacturer's recommendations, which prevented the side brace lock link from moving to the over center down and lock position. Functional checks, as required by the manufacturer's maintenance instructions, were not accomplished after this adjustment.