You don't need to boil spareribs before grilling because you can make tender, juicy, delicious ribs without boiling them. Many grilling and barbecue enthusiasts will tell you the length of time you should boil ribs before cooking is zero minutes. Some cooks prefer to boil ribs before cooking and a typical time, with the ribs fully submerged in salted water, is around 45 minutes to an hour on a medium-low simmer. While boiling does have some advantages over straight grilling, it has a significant downside.
One advantage boiling has over straight grilling is cooking time. With a 45-minute to one-hour boil first, the spareribs will tenderize in the boil and need only go onto the grill to sear and caramelize on their exterior-- a process that only takes about 10 to 15 minutes, per side, over a medium-hot grill. On the other hand, grilled ribs, which should be cooked with medium, indirect heat on the grill, will take anywhere between two and three hours or more to become fully tender.
With boiling, ribs can be cooked ahead of time to tenderize and stashed in the refrigerator. Later, the ribs can simply be put on the grill to sear and caramelize when you are ready. This is handy when for busy weeknights, tailgating or other occasions when you do not have time to nurse ribs on a grill for hours.
Consistency and Monitoring
Monitoring and maintaining low heat on a grill, especially a charcoal grill, can be an arduous task. With straight grilled spareribs, if the grill is too hot, your ribs will not become tender, and if the grill isn't hot enough, the ribs will take seemingly forever to cook. Boiling removes this problem and the need for constant monitoring because the ribs only need a relatively quick sear on the grill after they've been boiled.
Flavor and Texture
The biggest drawback with boiling is flavor. Boiling cooks away much of the fat and protein in the ribs. What you're left with after boiling are tender spareribs that generally don't have much flavor. While this will allow your barbecue sauce or dry rub to really shine, your spareribs will be lacking in classic grilled pork flavors. Similarly, boiling the spareribs before grilling will give tender results. But for many barbecue enthusiasts, ribs that are too tender, verging on mushy, are generally a bad thing. Classic barbecue spareribs should have some give and tenderness, but the ribs should still have a toothsome chew. Unfortunately, boiling can often cook this texture out.
Alternative to Boiling
If you would like to get some of the benefits of boiling -- such as consistency and the ability to partially cook the spareribs ahead of time -- without a significant loss of flavor, consider roasting the ribs in the oven before grilling. To pre-roast spareribs, place the ribs on a large cooking sheet and cover the entire sheet and ribs with aluminum foil. Bake the spareribs, in a 350-degree Fahrenheit oven, for 1 1/4 to 1 1/2 hours, or until tender. The spareribs can then be finished off by caramelizing them on the grill over medium heat for five to 10 minutes per side.