You have to pay attention. Large sea scallops are usually about 2 inches. Once they are darkened on both sides and look almost opaque in the midsections, don’t hesitate...pull them off the grill. One of the two best recipes from 25 Essentials – Techniques for Grilling Fish by Karen Adler and Judith Fertig. The other one: recipe #514042. Note: Can use a cast iron skillets on the grill. Good to know.