Add your live Dungeness crab to the pot and let simmer. Dungeness crabs that weigh 1 ½ to 2 ½ pounds should boil for about 15 minutes, while crabs weighing around 3 pounds can boil for 20 minutes. Drain the pot and rinse crabs with cool water for a few seconds to be able to immediately handle them. Crack those legs, then you’re done!