In a 2 to 3-quart pan, combine catsup, water, sherry, worcestershire, onion, lemon, garlic, and butter.
Bring to a boil over high heat; then reduce heat and simmer, uncovered, stirring occasionally, for 30 minutes.
Brush ribs with sauce.
Barbecue ribs by indirect heat
Place ribs, fat side up, on grill directly above drip pan.
Cover barbecue; adjust dampers as necessary to maintain an even heat.
Cook ribs, brushing occasionally with sauce, until meat near bone is no longer pink; cut to test (1 to 1 1/4 hours).