Mercury – Malfunction Light Harness | 40-Foot Single-Helm Cable | 84-8M0048058

Overview

Large boats with long console runs or deep rigging channels often need more reach than a standard harness can offer. The Mercury 84-8M0048058 Malfunction Light Harness provides a full 40 feet of length, giving you plenty of room to route the catalyst-warning signal from the engine compartment all the way to the helm. Once in place, it ensures the dash-mounted malfunction light responds immediately whenever the catalyst system detects an issue—just like a check-engine light on a car.

Key Features

• 40-Foot Harness – Longest single-helm option for large boats and extended rigging paths.
• OBDM Alert Delivery – Sends catalyst-system warnings straight to the dash-mounted indicator light.
• Catalyst-Compatible – Works on all MerCruiser engines equipped with a catalyst system.
• OEM Mercury Connectors – Factory-fit ends ensure proper alignment and a secure connection.
• Flexible Routing Length – Ideal for extended cabins, deep-V hulls, and complex helm layouts.
• Reliable Fault Notification – Ensures your dash light triggers the moment the system detects a catalyst malfunction.

Compatibility

• All catalyst-equipped MerCruiser engines
• Dash-Mounted Catalyst Malfunction Light (8M0046481)
• Single-helm installations requiring a 40-foot harness

Performance & Practical Benefits

This long harness gives you the freedom to route the malfunction-light circuit cleanly through bulkheads, under decking, and along long rigging corridors. Once connected, the catalyst light provides an immediate visual cue when the emissions system needs attention, helping you address issues early and avoid more serious problems down the road. On larger boats where access can be tight, this extra cable length keeps the installation clean and stress-free.

Why Buy OEM

Catalyst alerts are too important to trust to generic wiring. Mercury’s OEM harness is built with proper shielding, correct pinout, and marine-grade connectors designed to stand up to vibration, moisture, and engine-room heat. Aftermarket harnesses can cause false alarms or—worse—fail to trigger the light at all. The factory version ensures dependable communication every time you turn the key.

FAQ

Q1: What does this harness connect?
It links the engine’s OBDM catalyst-alert circuit to the dash-mounted malfunction light.

Q2: Why choose the 40-foot version?
It’s ideal for large boats or long helm layouts where shorter harnesses can’t reach cleanly.

Q3: Will this work on all MerCruiser engines?
It works on any MerCruiser engine equipped with a catalyst system.

Q4: Does this include the malfunction light?
No. The light is sold separately as part number 8M0046481.

Q5: Is installation difficult?
No. It uses OEM connectors and routes like any standard helm harness—just with more length to manage.