Murakami claimed silver and Hurd the bronze.
Taking gold were the heavily fancied Chinese, while Mexico claimed silver and the US took bronze.
He touched out U.S. teammates Anthony Ervin, 33, and Nathan Adrian, who claimed silver and bronze.
Bahrain's Eunice Jepkirui Kirwa claimed silver while the Ethiopian Mare Dibaba took bronze.
Earlier in the night Mitch Larkin claimed silver for Australia in the men's 200m backstroke.
Her American rival, Sarah Hammer, claimed silver ahead of the Belgian Jolien D'Hoore.
Ireland's Martyn Irvine claimed silver in the men's 15km (60-laps) scratch race as Ivan Kovalev of Russia won gold.
In that even he claimed silver in London and also set the world record at the 2013 world championships.
"He's the best dinghy sailor the world has ever seen," said Railey, who was himself delighted to have claimed silver.
Germany won gold for the second successive Olympics as they scored 72.916 per cent overall, while the Netherlands claimed silver with 71.750 and Denmark took bronze with 68.875.
Although an Olympic gold medal eluded him throughout his career, he claimed silver in the giant slalom and supergiant slalom at the 1992 Winter Games in Albertville, France.
