New York - Fire exploded a fuel tank aboard a Navy radar picket ship at dawn yesterday, killing three men and injuring two others.  The fire was brought under control six hours later.
     The stricken ship, the Searcher, was on station at sea 125 miles southeast of here.  Navy and Coast Guard vessels rushed to her aid.
     An amphibious plane flew three of the most severely injured men to New York City.  One died on the way to the Naval Hospital at St. Albans, Queens.
                                Bodies Carbonized
     The bodies of the two others killed in the blaze were "completely carbonized," the Navy said. 
     The Searcher had recently started a new tour of patrol duty off the Atlantic coast east of Cape May, N.J.
     A converted Liberty ship, she is crammed with expensive radar equipment.  It cost four million dollars to fit her out for this job.
     Because of her long periods of patrol duty, the picked ship carried large supplies of fuel oil.  
     The fire broke out in the starboard tank and roared with intense heat through the engine room on the second deck and the midship superstructure.  The Navy called the damage moderate.
     Lt. Cmdr. William E. Chapline, pilot of a rescue plane, said, "the paint was all burned off by the engine room, as evidence of the intense heat."
     After the fire was extinguished, tugs began to tow the powerless 416-foot vessel to port.  She was expected to reach New York by this afternoon.
The Searcher's Captain is Cmdr. James A. Paulick, 32, who lives at Newport, R.I., where the Searcher is based.  His home town is Minneapolis.
     The fatally injured man who died ashore was identified as Dennis Cook, a Fireman, of Milligan College, Tenn.
     The Navy announced that "presumptive" identification of the two other dead was made on the basis of the ship's muster.  It withheld the names pending positive identification.
     The two injured men are Calvin H. Crisp, 27, a Boiler Tender, whose wife, Sally Jo, lives at Newport, R.I., and Lelond Terry, Fireman, whose wife, Ellaquay lives at Memphis, Tenn.