Mercury – Outer Helm Extension Harness | 70-Foot Extension | 84-8M0173573

Overview
This 70-foot extension harness is built for the biggest, widest triple- and quad-engine boats—setups where the outer engines sit so far outboard that even long standard harnesses won’t reach cleanly. When the wiring path winds through long tunnels, bulkheads, or deep rigging channels, this extension keeps you from stretching or forcing the harness. It lets the wiring run in a smooth, natural line, which helps the controls stay steady and predictable. On large offshore rigs, this extra length makes rigging and later service a whole lot easier.

Key Features
    • 70-Foot Extension – Long reach for very wide transoms and extended routing paths.
    • Outer-Engine Use – Made for the outside engines on triple and quad DTS systems.
    • OEM Connectors – Factory ends that snap in firmly and stay locked.
    • Flexible Routing – Helps avoid pinch points, sharp turns, and over-stressed wiring.
    • Stable Control Path – Keeps throttle and shift signals clean over long distances.

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

Performance & Practical Benefits
On large offshore hulls, this extension stops the harness from being wedged into cramped spots or pulled across long, awkward routes. The controls feel smoother because the wiring isn’t kinked or stretched to reach. You also end up with more breathing room in the rigging bay, which makes inspections and servicing a lot easier. For big multi-engine layouts, the extra slack keeps the whole system calmer.

Why Buy OEM
OEM wiring holds up to vibration, heat, and saltwater better than generic cable. The connectors match Mercury’s system exactly, which means fewer loose connections and far fewer electrical gremlins. It’s dependable rigging made for real marine use.

FAQ
Q1: How do I know I need the 70-foot version?
A: If your outer-engine run is extremely long and shorter extensions still leave you short or pulled tight, this is the right length.

Q2: Any setup needed?
A: Nope—just plug it in and route it cleanly.

Q3: Is it good for saltwater?
A: Yes. A quick rinse now and then keeps the connectors in good shape.

Q4: Any installation tips?
A: Use wide, gentle curves and avoid rubbing points along the hull.

Q5: What are early signs of wear?
A: Sluggish controls, intermittent signals, or visible jacket scuffing along the run.