boil lobsters for 10 to 20 min, depending on size: note the time at which the water comes to a boil again. from that point, boil the lobsters for 10-20 minutes or longer, depending on the size of the lobster. 10-13 minutes for 1 lb lobster, 12-18 minutes for a 1 1/2 pound lobster, 18-23 minutes for a 2-3 pound lobster.