Mercury - Engine to Vessel Interface Panel Extension Harness 10 Foot Sterndrive Harness Extension 84-879312T01. The Mercury Engine-to-Vessel Interface Panel (VIP) Extension Harness is designed for diesel sterndrive installations where the vessel interface panel is mounted farther from the engine. It provides a factory-correct extension between the engine and VIP without modifying, cutting, or stressing the original harness.. The 10-foot length allows relaxed, clean routing through larger engine