2. However, the steaming time of hairy crabs is related to their size. For example, crabs with a weight less than 3 should be cooked and steamed for 10 minute, crabs with a weight of 4 should be cooked and steamed for 12 minute, and crabs with a weight greater than 4 need about 15 minute. Generally, it takes two minutes to extend the time every one or two minutes.