Engine Wiring Harnesses for Mercruiser Sterndrives bpiicpower››Mercruiser Sterndrives›Electrical SystemWiring Harness, adapter to convert OMC/Mercruiser to 8 prong rectangular female plug, 23' Red/Black wires - 10 Gauge all other wires - 16 Gauge Round plug has 2 Large Pins and 7 Small Pins Note: This.. mercruiser wiring harness | eBay www›Search›mercruiser wiring harnessFind great deals on eBay for mercruiser wiring harness. Shop with confidence. Skip to main content. eBay Logo: Mercruiser/Mercury Main Electrical Instrument Wiring Harness Cable 84-806391A1 See more like this. Mercruiser 5.0 5.7 Wire Wiring harness 84-98423A5 Late 1980s. Pre-Owned. $69.