Mercury – Inner Helm Extension Harness | 20-Foot Extension | 84-8M0159759

Overview
This 20-foot inner-engine extension harness gives you extra reach for the inside engines on triple- and quad-engine boats. When the standard harness won’t quite make the run—or the routing path ducks around bulkheads—this length keeps you from stretching the wiring or forcing tight bends. It lets the harness run in a smoother line so the controls feel steady. On larger multi-engine rigs, that extra room makes rigging and service a lot easier.

Key Features
    • 20-Foot Extension – Adds enough slack for longer inner-engine routing.
    • Inner-Engine Use – Made for the inner engines on triple and quad DTS setups.
    • OEM Connectors – Factory ends that snap in tight and stay locked.
    • Easier Routing – Helps avoid pinched spots and sharp corners.
    • Steady Signal Path – Keeps throttle and shift response smooth.

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

Performance & Practical Benefits
The extra length keeps the harness from getting jammed into tight corners, which helps the controls feel more natural. It also makes the rigging bay easier to work in, giving you more space to move during service. On bigger boats, a little added slack helps the whole system feel calmer and less cramped. You end up with cleaner wiring and fewer small issues later on.

Why Buy OEM
OEM harnesses hold up well to vibration, heat, and saltwater, and the connectors match Mercury’s design exactly. That means fewer loose plugs and fewer weird glitches down the road. It’s reliable wiring built for real-world marine use.

FAQ
Q1: How do I know I need the 20-foot version?
A: If your inner-engine harness is tight or won’t reach cleanly on a wide or complex rigging path, this length usually fixes it.

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

Q3: Saltwater safe?
A: Yes. A quick rinse and occasional connector check keep it in good shape.

Q4: Any installation tips?
A: Use smooth, gentle curves so the harness isn’t under tension.

Q5: What are signs of wear?
A: Hesitant controls, intermittent signals, or jacket rubbing along tight spots.