8M0121257 Mercury Coil 1&4 | Genuine Used Part

🔧 Product Description

Genuine Mercury Ignition Coil - Part Number: 8M0121257

A genuine Mercury ignition coil used on selected Yamaha-based Mercury / Mariner four-stroke outboards. This coil is commonly identified as the coil for cylinders 1 and 4 in compatible 115HP four-stroke ignition systems and is part of the 880892T / 8M0121257 supersession family.

⚙️ Key Features

• Genuine Mercury ignition coil

• Correct Mercury part number 8M0121257

• Replaces earlier 880892T ignition coil reference

• Commonly used for cylinder 1 and cylinder 4 positions

• Cross-references with Yamaha 68V ignition coil family

🔄 Supersession & Cross Reference

OEM Supersession Chain:

• 8M0121257 → Supersedes 880892T

• 880892T earlier Mercury ignition coil reference

OEM / Related Numbers:

• 8M0121257

• 339-8M0121257

• 880892T

• 339-880892T

• 888309 related coil reference

• Yamaha: 68V-82310-00-00

• Yamaha: 68V-82310-01-00

• Yamaha: 69J-82310-00-00

Aftermarket / Verified Equivalents:

• WSM: 380-5122

• Aftermarket Mercury / Yamaha coil replacements for 339-880892T

• Aftermarket Yamaha / Mercury F115 / F200 / F225 coil replacements

🚤 Compatibility

Commonly used on:

• Mercury / Mariner Yamaha-based four-stroke ignition systems

Typically suits:

• Engine models:

• Mercury 115 EFI FourStroke - 2001

• Mercury 115 EFI FourStroke - 2002

• Mercury 115 EFI FourStroke - 2003

• Mercury 115 EFI FourStroke - 2004

• Mercury 115 EFI FourStroke - 2005

• Mercury 115 EFI FourStroke - 2006

• Mercury 225HP 4-stroke EFI applications using shared Yamaha-based coil family

• Yamaha F115 / LF115 ignition systems using 68V coil family

• Yamaha F200 / F225 4-stroke ignition systems using related 68V / 69J coil family

• HP Range: commonly 115HP - 225HP shared Mercury / Yamaha four-stroke coil family

• Engine Type: Mercury / Yamaha-based EFI four-stroke outboard

• Year Range: approximately 2001 - 2006 for core Mercury 115 EFI FourStroke applications, with broader Yamaha-family use through 2015 where specified

• Serial Note: Match by cylinder position, coil number, engine serial number and connector style.

🔌 Function

The ignition coil converts ECU-triggered low-voltage input into high-voltage spark output for the assigned cylinders.

Common signs of failure:

• Misfire on cylinder 1 or 4

• Weak or no spark

• Engine runs rough under load

• Coil fault follows when swapped between cylinders

• Hard starting after plug replacement

• ECU ignition fault code

• Cracked, swollen or corroded coil body

📦 Condition

• Genuine used part

• Removed from running engine where applicable

• In good working condition unless otherwise stated