Mercury – Outer Helm Extension Harness | 40-Foot Extension | 84-8M0159756

Overview
This 40-foot extension harness is built for wide transoms and long rigging runs on triple- and quad-engine boats. When the outer engines sit way outboard and the factory harness just won’t reach comfortably, this piece gives you the distance you need without stretching or forcing the wiring. It lets the harness follow a smoother path so everything feels calmer at the helm. On big offshore rigs, that extra room makes rigging and service work a whole lot easier.

Key Features
    • 40-Foot Extension – Long reach for the largest hulls and wide-beam layouts.
    • Outer-Engine Use – Built for the outer engines in triple and quad DTS setups.
    • OEM Connectors – Factory ends that snap in solid and stay locked.
    • Flexible Routing – Helps avoid kinks, pinched runs, and stressed wiring.
    • Steady Control Path – Supports smooth throttle and shift communication.

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

Performance & Practical Benefits
With this much length to work with, the harness can take a relaxed route instead of being shoved into tight corners. That keeps control inputs feeling smooth and predictable because the wiring isn’t under strain. It also leaves more room in the rigging bay, making inspections or service work far less frustrating. On big boats, this extension simply makes everything feel cleaner and easier to manage.

Why Buy OEM
OEM harnesses hold up to vibration, heat, and saltwater better than generic cables. The connectors fit exactly the way Mercury designed, so you’re not chasing odd glitches or loose plugs. It’s wiring made for real-world use and long-term reliability.

FAQ
Q1: How do I know I need the 40-foot version?
A: If your outer engines sit far outboard and the standard harness won’t reach cleanly, this is the length that fixes it.

Q2: Any special setup required?
A: No—just plug it in and route it.

Q3: How does it hold up in saltwater?
A: Very well. A quick rinse now and then keeps everything in good shape.

Q4: Any installation advice?
A: Keep the path smooth with wide curves and avoid rubbing points along the hull.

Q5: What are signs the harness may be wearing out?
A: Hesitant controls, signal dropouts, or visible jacket wear.