Mercury - Quicksilver Blue Wire Spark Plug Wire Kit V8 High-Performance Ignition System Marine Grade 847701Q7. Overview. The Quicksilver 847701Q7 Blue Wire Spark Plug Wire Kit is designed for V8 MerCruiser high-performance engines-including 454, 502, 540, and 572 CID models equipped with Thunderbolt IV ignition systems (1990 and newer). Built by Mercury Marine, this OEM wire set delivers strong, consistent spark even under the toughest conditions. Each wire is factory-cut to exact length and fit