Mercury – Inner Helm Extension Harness | 30-Foot Extension | 84-8M0159761

Overview
This 30-foot inner-engine extension harness is made for boats where the inside engines sit far enough away that the standard harness just won’t reach cleanly. On wide transoms or long routing paths, it keeps you from stretching the wiring or forcing sharp corners. Instead, it lets the harness follow a smoother line so the controls feel steady and predictable. It’s a simple way to make big multi-engine setups easier to rig and service.

Key Features
    • 30-Foot Extension – Gives plenty of reach for longer inner-engine runs.
    • Inner-Engine Use – Designed for inner engines on triple and quad DTS layouts.
    • OEM Connectors – Factory ends that snap in tight and stay secure.
    • Smoother Routing – Helps avoid pinch points and tight bends.
    • Consistent Control Path – Keeps throttle and shift communication reliable.

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

Performance & Practical Benefits
With the extra length, the harness can sit in a relaxed route instead of being squeezed around corners. That usually means smoother throttle and shift feel because nothing is kinked or under tension. It also opens up space in the rigging bay, which makes routine checks and service a lot easier. On large offshore hulls, the difference in day-to-day usability is noticeable.

Why Buy OEM
OEM wiring holds up better to vibration, heat, and saltwater than generic extensions. The connectors fit exactly the way Mercury designed, reducing odd glitches and loose connections. It’s dependable if you want the system to stay stable long-term.

FAQ
Q1: How do I know I need the 30-foot version?
A: If your inner-engine harness still feels tight after routing, or you’re coming up short on a wide-beam rig, this length usually solves it.

Q2: Any setup after plugging it in?
A: No—just connect it and route it.

Q3: How does it hold up in saltwater?
A: Very well. Just rinse now and then and check the connectors.

Q4: Any installation tips?
A: Use wide, smooth bends so the harness isn’t strained or rubbing.

Q5: What are early signs of wear?
A: Hesitant controls, intermittent signals, or areas where the jacket shows rubbing.