Mercury – Inner Helm Extension Harness | 25-Foot Extension | 84-8M0159760

Overview
This 25-foot inner-engine extension harness gives you the extra room needed to reach the inside engines on triple- and quad-engine boats. When the standard harness comes up short—or the rigging path winds through bulkheads or tight corners—this extension keeps things from getting stretched or pinched. It lets the wiring settle into a smoother route, which helps the controls feel more natural. On larger multi-engine rigs, that extra slack makes rigging and later service a lot less aggravating.

Key Features
    • 25-Foot Extension – Adds solid extra reach for longer inner-engine runs.
    • Inner-Engine Use – Made for the inside engines on triple and quad DTS setups.
    • OEM Connectors – Factory ends that seat firmly and stay locked.
    • Smooth Routing – Helps avoid sharp bends and tight squeeze points.
    • Reliable Signal Path – Keeps throttle and shift communication steady.

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

Performance & Practical Benefits
The extra length helps the harness follow an easier path instead of being forced through cramped spots. You’ll usually feel smoother control response because the wiring isn’t kinked or under tension. It also opens up the rigging bay so service work isn’t such a tight squeeze. On wide-beam offshore boats, that extra space makes the whole setup feel cleaner and more predictable.

Why Buy OEM
OEM wiring handles vibration, heat, and saltwater better than generic cable. The connectors are the exact match for Mercury’s system, which helps prevent loose plugs, glitches, and signal dropouts. It’s long-lasting rigging built for real marine use.

FAQ
Q1: How do I know I need the 25-foot version?
A: If your inner-engine run still feels tight with shorter extensions, this length usually gets you the clean routing you need.

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

Q3: Is it OK for saltwater boats?
A: Yes. A quick rinse and connector check now and then keeps it in good shape.

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

Q5: What are signs the harness may be wearing out?
A: Hesitant controls, intermittent signals, or visible jacket wear along tight spots.