Mercury Marine, Mercury Racing, and Mariner high-performance 2-stroke V6 EFI outboards—including the 2.0 L, 2.4 L, and 2.5 L platforms—depend on the 16-pin ECU harness connector for precise electronic communication between the engine control unit and systems such as ignition and fuel injection.
These engines include popular models like the V‑150 HP, V‑175 HP, V‑200 EFI, XRi (front-injected), Laser EFI, Race ROS (side-injected), S3000, F1, Champ, 260 ROS, 280 EFI, and 300 Drag. In all configurations, secure ECU connectivity is essential for performance, reliability, and fuel system operation.
Ring-Coupling Nut: Purpose and Compatibility
The ECU ring-coupling nut secures the 16-pin harness to the ECU, locking it in place to prevent disconnection due to vibration or heat cycling. Over time, the factory nut can become brittle or crack, risking signal loss or fuel delivery issues. The OEM replacement nut—Mercury part number 19049 (also listed as 190491)—restores a firm, factory-spec connection.
This nut is compatible with the following Mercury OEM ECU harness part numbers: 98866, 98866A27, 98866A26, 98866A14, 98866A25, 98866A9, and 454‑9602.
Key Features and Technical Benefits
This Mercury OEM ECU connector nut delivers the following performance advantages:
OEM Fit and Reliability: Engineered to match original specifications for all 16-pin Mercury EFI harness connections.
Durable Construction: Designed to withstand heat, vibration, and marine environmental stress without cracking or fatigue. Outlasts the earlier Gray Conector Nuts.
Tool-Free Installation: Snaps securely into place for fast, stable installation.
UL Rated & RoHS Compliant: Built to meet industry safety and environmental standards.
Installation Instructions
Remove the damaged or worn factory nut.
Check alignment and orientation of the replacement nut.
Press to snap the new nut evenly into place.
Once secured, the nut will remain locked until manually removed.
Keeping a spare on hand is recommended to prevent downtime and maintain proper ECU connectivity in high-performance applications.
Technical Note: Dielectric Grease Warning
Buckshot Racing #77 has emphasized a critical maintenance advisory. Mercury Hi‑Performance had confirmed that the use of dielectric grease on the 16-pin ECU connector in digital EFI systems—specifically across the 2.0 L, 2.4 L, and 2.5 L V6 engines—can interfere with electrical contact. This issue primarily affects the fuel pump power circuit. Mercury Racing officially discontinued the use of dielectric grease on these connectors. For best results and full electrical integrity, all ECU connectors must be installed clean and dry, with no insulating compounds.
Whether you're maintaining a 260 ROS, tuning a 280 EFI, or racing with a 300 Drag, a secure ECU harness connection is vital for proper engine management. The Mercury ECU ring-coupling nut (part 19049 / 190491) ensures that your EFI system performs as intended—delivering stable fuel pump operation, accurate ignition timing, and reliable engine control across Mercury Marine, Mercury Racing, and Mariner 2-stroke V6 EFI outboards.
(Compared to Mercury OEM MSRP of $17.83, Sourced Direct)
Contact Mike Hill at mike@buckshotracing77.com or +1-714-697-1716 for tech support