Place meat, fat side up, on a rack in a roasting pan. Sprinkle with pepper. Insert a meat thermometer into the meat. Place pan on the grill rack, but not over the coals. Lower the grill hood. For medium doneness, cook for 2-1/4 to 3-1/4 hours or until meat thermometer registers 145 degrees F. (temperature will rise 5 degree F after it's removed from the grill). Add extra coals as needed to maintain temperature. Baste with reserved marinade.