The Genuine Sierra 18-7968 Spin-On Fuel Filter is a premium OEM-quality replacement for Mercury 18458A4 / 35-18458Q4, engineered specifically for Mercury EFI and DFI (Optimax) outboards (1996 and newer). This filter provides 10-micron filtration, protecting critical fuel system components by removing fine debris and water before fuel reaches injectors and pumps.
At Buckshot Racing #77, we supply genuine Sierra marine filters trusted for consistent performance, reliability, and correct fitment in high-demand marine environments.
Designed for Mercury EFI, XRI, and Optimax Systems
Fuel-injected Mercury outboards rely on high-pressure fuel systems, making filtration critical. The Sierra 18-7968, replacing Mercury 18458A4, is designed for VST-mounted spin-on applications, commonly found on EFI and DFI engines.
This includes late-model XRI systems, 2.5L EFI engines, and all 3.0L Optimax platforms, where clean fuel is essential to prevent injector clogging, lean conditions, and performance loss.
Verified Fitment Across Mercury Outboards (115–300 HP)
This filter fits a wide range of Mercury V6 fuel-injected outboards, particularly 1996 and newer EFI and DFI engines.
Mercury 2.5L EFI and XRI platforms, including 150 EFI, 175 EFI, 200 EFI, and later 200 XRI systems, as well as performance engines like 200 Pro Max and 225 Pro Max.
It is also used on Mercury 3.0L DFI/Optimax engines, including 225 Optimax, 250 Optimax, 250XB, 300 Optimax, 300 Pro Max, 300X, and early 300XS platforms.
Additionally, it fits Mercury SportJet 240 EFI (1996–2000) and other Mercury EFI systems equipped with the spin-on VST filter base.
While early 2.4L EFI and early XRI engines (pre-1996) often used different filter designs, many have been updated or converted to this spin-on system, making the 18458A4 / 18-7968 one of the most commonly used filters in modernized legacy builds.
Spin-On Design for Quick, Reliable Service
The spin-on design allows for fast and clean replacement during routine maintenance. The integrated gasket ensures a tight, leak-free seal, while the metal canister is built to handle heat, vibration, and marine exposure.
Routine replacement is critical for maintaining fuel pressure, injector performance, and engine reliability, especially when running ethanol-blended fuels.
Cross-Reference Part Numbers
The Sierra 18-7968 replaces and cross-references: Mercury / Quicksilver: 18458A4, 35-18458Q4, 35-18458T4, 184585, Sierra: 18-7968, Mallory: 9-37806
Why Fuel Filter Maintenance Matters
A clogged or contaminated filter can cause:
- Lean fuel conditions
- Injector damage
- Hesitation or RPM loss
- Hard starting or stalling
Replacing the filter regularly ensures clean fuel delivery, consistent pressure, and optimal engine performance, especially in high-performance applications.
OEM-Quality Filtration You Can Trust
The Genuine Sierra 18-7968 Spin-On Fuel Filter, replacing Mercury 18458A4, is the correct solution for maintaining Mercury EFI, XRI, and Optimax fuel systems (115–300 HP).
At Buckshot Racing #77, we provide trusted marine components designed to keep your engine running clean, efficient, and performing at its best—whether you're running a 150 EFI fishing motor or a 300X high-performance build.