The Mercury 98866A25 ECU and injector harness assembly is a key component for proper fuel delivery and engine performance in Mercury Marine 2.5L V6 EFI and XRI outboards. This harness provides the electrical link between the ECU and fuel injectors, ensuring accurate signal transmission, consistent injector timing, and reliable operation across the RPM range.
At Buckshot Racing 77, our harnesses are custom made in the USA by Rotger Racing, using high-quality, marine-grade materials designed for durability in high-performance environments. Whether restoring a stock engine or building a race setup, a reliable harness is essential.
Why the ECU & Injector Harness Matters
The ECU in Mercury 2.5L EFI and XRI engines depends on clean electrical signals to control injector pulse and timing. A failing harness—often caused by heat, vibration, or corrosion—can lead to misfires, poor throttle response, or dangerous lean conditions.
Replacing the harness restores proper ECU-to-injector communication, improving consistency, throttle response, and engine reliability.
Fitment: Mercury 2.5L V6 EFI & XRI Outboards
This harness fits a wide range of Mercury 2.5L V6 EFI and XRI engines, including models such as the V-150 XRi, V-175 XRi, and V-200 XRi, along with performance variants like the 150 EFI Pro Max, 200 EFI Pro Max, and 200 Super Magnum.
It is also compatible with V-175 (Ski), V-175 Magnum, V-200, and V-200 Magnum engines that share similar EFI/XRI wiring architecture. These engines are commonly used in bass boats, performance hulls, and recreational setups.
This harness is typically found on engines within the D008200 and newer serial ranges, though compatibility may vary by EFI configuration. Always confirm fitment by serial number.
Two Harness Options Available
We offer two configurations to match your engine setup and ECU requirements.
1) Race Harness (Merc A6, Brucato ACU, PPE ECU)
The Race Harness is built for high-performance engines using aftermarket ECU systems such as Mercury A6, Brucato ACU/PCU, and PPE. It eliminates non-essential circuits, excluding TPS, head temperature, and fuel pump wiring, resulting in a simplified, lightweight design.
This setup is ideal for race engines, modified builds, and custom fuel systems where reliability and simplicity are priorities.
2) Stock Harness (Laser EFI, XRI, Front Injection)
The Stock OEM Replacement Harness is a direct-fit solution for factory Mercury Laser EFI, XRI, and front-injected systems. It retains all critical circuits, including TPS, head temp, and fuel pump wiring, ensuring proper ECU control and engine monitoring.
This option is best for stock or lightly modified engines requiring full functionality and dependable operation.
Installation & Reliability Notes
Proper routing and secure installation are essential. Keep the harness away from heat and moving components, and ensure all connections are clean and corrosion-free. Applying dielectric grease helps protect terminals and maintain long-term reliability.
Performance Benefits
A high-quality harness improves idle quality, throttle response, and fuel delivery consistency. In performance applications, it reduces the risk of lean conditions and engine damage. For recreational use, it restores dependable operation and eliminates common wiring-related issues.
Built in the USA for Performance
Each harness from Buckshot Racing 77 is custom-built in the USA by Rotger Racing, delivering superior durability and performance compared to aging OEM wiring.
Choosing the right harness—Race or OEM—ensures your Mercury 2.5L EFI engine runs reliably and performs at its best.