Mercury – Outer Helm Extension Harness | 15-Foot Extension | 84-8M0159751

Overview
This 15-foot extension harness gives the outer engines on triple- and quad-engine boats the extra reach they usually need. Long runs and wide transoms can make the factory harness feel tight, and this extension keeps you from forcing sharp bends or stretching the wiring. It lets the harness take a smoother, more relaxed path from the helm to the outer engines. It’s a simple add-on that makes big multi-engine layouts much easier to rig and service.

Key Features
    • 15-Foot Extension – Adds generous length for wide transoms and long routing paths.
    • Outer Engine Use – Designed for the outside engines in triple and quad setups.
    • OEM Connectors – Factory plugs that snap in securely and stay locked.
    • Flexible Routing – Helps avoid tight corners, pinched sections, and pulled wiring.
    • Stable Signal Path – Keeps throttle and shift communication steady.

Engine & Boat Compatibility
    • Triple engine
    • Quad engine
    • Outer-engine helm pathways

Performance & Practical Benefits
With more length to work with, the wiring can follow a natural path around the boat instead of squeezing through tight areas. That usually gives the controls a smoother, more predictable feel because the harness isn’t kinked or under strain. It also keeps the rigging bay more open and easier to navigate when you’re doing service work. For wide-beam boats, the extra room makes a noticeable difference.

Why Buy OEM
OEM wiring holds up to vibration, heat, and salt spray better than off-brand extensions. The connectors match Mercury’s design exactly, so you avoid loose plugs and random glitches. It’s wiring you can count on for the long haul.

FAQ
Q1: How do I know I need this extension?
A: If the outer engines on your triple or quad setup feel tight to route, this 15-foot extension usually solves the reach issue.

Q2: Does it require calibration or setup?
A: No—just plug it in and it extends the harness cleanly.

Q3: How does it handle saltwater?
A: Fine—rinse occasionally and keep an eye on the connectors.

Q4: Any installation tips?
A: Give it a relaxed path with smooth bends so the harness isn’t pulled tight.

Q5: What are signs it may be wearing out?
A: Hesitant controls, intermittent signals, or spots where the jacket is rubbing thin.