Mercury – Tachometer Harness | Engine Gauge Wiring | 84-827593A2

Overview
This bullet-pin tachometer harness is the simple plug-in lead used on many mid-size Mercury and Mariner tiller engines. It ties the tach straight into the engine’s signal wire without extra adapters or guesswork. On the water, it helps the tach read clean and steady so you can keep an eye on RPM while running a tiller rig. It’s a small part, but it makes a big difference when your gauge depends on a solid signal.

Key Features
    • Bullet-Pin Connector – Classic single-pin tach signal style.
    • Direct Tach Lead – Sends a clean RPM signal from engine to gauge.
    • OEM Wire Colors – Matches Mercury’s standard wiring layout.
    • Flexible Jacket – Handles tiller vibration and engine movement.
    • Quick Install – Plugs straight into the engine harness.

Engine & Boat Compatibility
    • Mercury 30 HP electric-start tiller
    • Mercury 40 HP electric-start tiller
    • Mercury 50 HP electric-start tiller
    • Mercury/Mariner 60–90 HP electric-start tiller models

Performance & Practical Benefits
This harness helps keep the tach steady, especially on tiller boats where vibration and engine movement are constant. It keeps the RPM signal clean so the gauge doesn’t flicker or drop out. Installation is quick—plug it in, route it cleanly, and you’re set. It’s a must-have when adding a tach to older tiller engines or replacing a worn lead.

Why Buy OEM
OEM harnesses follow Mercury’s wiring pattern exactly, which means no pin guessing, no color confusion, and no poor-quality connectors. They’re built to survive real engine vibration and moisture better than generic versions. With OEM, the tach works right the first time.

FAQ
1. How do I know if my tach harness is failing?
If the tach drops out, jumps around, or reads nothing, the harness may be loose or worn.

2. Do I need to calibrate the tach after installing this?
No—once it’s plugged in, the tach should read normally if the gauge is set correctly.

3. How does it handle wet conditions?
It holds up well; just keep the connector clean and protected from corrosion.

4. Anything important during installation?
Make sure the bullet connector seats firmly into the engine harness—no wiggle.

5. What does a failing harness usually do underway?
Expect erratic RPM, dead readings, or a tach that cuts out during vibration.