Here's a useful, precise way of assessing doneness in scallops.
We typically recommend cooking scallops until their sides are firm and their centers are slightly translucent. Since determining whether the scallop’s interior is done requires cutting into it, we decided that it would be useful to have a more precise (and less destructive) way of assessing doneness. After searing a few batches, we determined that scallops are perfectly cooked when their centers reach 115 degrees. Because scallops are so small and are usually cooked over high heat, carryover cooking will add another 10 to 15 degrees, for an ideal final temperature of 125 to 130 degrees.