Mercury – Inner Helm Extension Harness | 70-Foot Extension | 84-8M0173576

Overview
This 70-foot inner-engine extension harness is meant for large triple- and quad-engine boats where the standard harness doesn’t come close to reaching the inner engines cleanly. Long routing paths, wide transoms, and deep rigging channels can make shorter runs feel tight or forced. This length lets the wiring relax into a smooth, natural route so the controls stay steady and predictable. On big offshore hulls, that extra reach makes rigging and later service a lot less painful.

Key Features
    • 70-Foot Extension – Built for the longest inner-engine runs.
    • Inner-Engine Use – For inner engines on triple and quad DTS setups.
    • OEM Connectors – Factory ends that snap in securely.
    • Flexible Routing – Helps avoid harsh bends and squeezed-in wiring.
    • Reliable Signal Path – Keeps throttle and shift communication clean and steady.

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

Performance & Practical Benefits
With this much extra length, the harness can follow an easy route instead of getting jammed through tight corners. That usually means smoother throttle and shift feel because the wiring isn’t kinked or strained. It also frees up space in the rigging bay, making inspections and service less of a wrestling match. On wide or deep boats, the difference in day-to-day use is noticeable.

Why Buy OEM
OEM wiring holds up to vibration, heat, and saltwater far better than generic harnesses. The connectors match Mercury’s design exactly, which helps prevent loose plugs and odd control glitches. It’s reliable, long-lasting rigging built for real marine conditions.

FAQ
Q1: How do I know I need the 70-foot option?
A: If shorter inner-engine extensions still feel tight or won’t reach cleanly, this is the length that usually solves it.

Q2: Any setup or calibration needed?
A: No—just plug it in and route it.

Q3: Is it safe for saltwater use?
A: Yes. Give it a rinse once in a while and keep an eye on the connectors.

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

Q5: What are early signs of wear?
A: Hesitant controls, intermittent signals, or areas where the jacket is starting to scuff.