In a food processor or blender purée chutney, orange juice, and barbecue sauce until smooth.
Thread four 12-inch skewers in the following order: pineapple, prawn, scallop, tomato, onion, prawn, scallop, tomato, onion, prawn, scallop, pineapple.
Brush skewers liberally with sauce and place in centre of cooking grate. Grill 6 to 8 minutes or until prawns are pink and scallops are opaque, turning and brushing liberally with sauce again halfway through grilling time. Serve with remaining sauce for dipping.