Mercury - Engine to Vessel Interface Panel Extension Harness 5 Foot Sterndrive Harness Extension 84-879312T. The Mercury engine-to-vessel interface panel (VIP) extension harness (5 foot) is designed for Mercury diesel sterndrive installations where the VIP is mounted away from the engine. It extends the factory wiring between the engine and the interface panel without cutting, splicing, or stressing original harness connections.. The five foot length is ideal for compact engine rooms and short r