Mercury – Outer Helm Extension Harness | 25-Foot Extension | 84-8M0159753

Overview
This 25-foot outer helm extension harness gives you the extra distance needed to reach the outer engines on wide-beam triple- and quad-engine boats. When the standard harness isn’t long enough—and the rigging path winds around bulkheads or across a wide transom—this extension keeps you from pulling the wiring tight. It lets the harness run in a smoother, more natural line, making the whole setup feel calmer and easier to manage. It’s a simple way to keep a big multi-engine layout from getting cramped.

Key Features
    • 25-Foot Extension – Extra-long reach for wide transoms and larger hulls.
    • Outer-Engine Use – Built for the outside engines on triple and quad setups.
    • OEM Connectors – Factory plugs that seat firmly and stay locked.
    • Flexible Routing – Helps avoid tight corners and pinched wiring.
    • Reliable Signal Path – Keeps throttle and shift communication steady.

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

Performance & Practical Benefits
With this extension in place, routing becomes a lot easier—especially on wide rigs where everything wants to be tight and squeezed. The extra length keeps the harness from kinking or stretching, which helps the controls feel more predictable. It also opens up the rigging bay so service work isn’t such a fight. On big boats, that extra room makes the whole setup feel cleaner and more manageable.

Why Buy OEM
OEM harnesses hold up to real marine punishment—vibration, heat, and salt spray—much better than generic wiring. The connectors fit exactly as Mercury designed, reducing the chance of loose plugs or random glitches. It’s dependable gear you won’t have to revisit later.

FAQ
Q1: How do I know I need the 25-foot version?
A: If your outer-engine harness comes up short or forces tight bends on a wide-beam triple or quad, this length usually solves it.

Q2: Do I need to configure anything?
A: Nope—just plug it in and it extends the run cleanly.

Q3: How does it hold up in saltwater?
A: Fine—rinse occasionally and keep an eye on the connectors.

Q4: Any install tips?
A: Route it with smooth, gentle curves to avoid stressing the harness.

Q5: What are early signs it may be wearing out?
A: Sluggish trim/controls, intermittent signals, or visible jacket rubbing.