The Mercury OEM 8M0207786 inline filter is used across a wide range of Mercury and Mariner two-stroke outboards. Depending on the engine, it may be found in the fuel, bleed, or oil-return system, which is why the same filter is sometimes described differently in parts catalogs.
The current Mercury part number is 8M0207786. It replaces earlier numbers including 8M0042285, 18206001, 18206, and 14991. Older service manuals and parts books may also show these with the Mercury prefix, such as 35-8M0207786, 35-8M0042285, 35-18206001, 35-18206, and 35-14991.
Mercury EFI, XRi & Pro Max Applications
This filter family is used on many classic Mercury EFI and bleed-system applications, including selected 150 EFI, 150 XRi, 175 EFI, 175 XRi, 200 EFI, 200 XRi, 220 Laser, 200 Pro Max, and 225 Pro Max engines.
On these earlier engines, the filter may be installed in a fuel or bleed circuit rather than in the later Optimax compressor oil-return system.
Because Mercury used several different layouts over the years, the exact function should be confirmed from the parts diagram for the specific engine and serial number.
Mercury Optimax, Pro XS & 300XS Applications
The 8M0207786 filter is also used on many 3.0L and 3.2L Optimax DFI engines, including selected 200, 225, 250 and 300 HP models.
Common applications include 200 Pro XS, 225 Pro XS, 250 Pro XS, 225 XS, 225 Sport XS, 250 Sport XS, 250 XS, and 300XS 3.2L engines.
On many of these Optimax and Mercury Racing DFI engines, the filter is used in the air-compressor oil-return circuit, and two filters are commonly installed in the system.
This is especially important during air-compressor service. If a compressor begins to deteriorate, small particles can enter the return circuit, so the filters and related hoses should be inspected carefully.
Other Mercury Applications
The same filter family also appears on selected 100, 115, and 125 HP four-cylinder two-stroke outboards, along with some 80 Jet, 105 Jet, and 140 Jet applications.
This wide usage is one reason the 8M0207786 part number shows up in several different Mercury systems and engine families.
Fuel Filter or Oil Filter?
The most accurate way to describe 8M0207786 is as a small Mercury inline service filter. On older engines, it may function as a fuel or bleed-system filter. On later Optimax DFI engines, it may be used in the compressor oil-return system.
That means it should not automatically be confused with the engine’s main fuel filter, water-separating filter, or remote oil-tank filter.
Why This Filter Matters
Although small and inexpensive, this filter protects narrow passages and critical components from contamination.
On EFI and bleed-system applications, it helps keep debris from moving through the circuit. On Optimax engines, it can help trap contamination in the compressor oil-return path.
A restricted filter can also affect flow, so replacement should be considered when servicing related components or when contamination is found.
Buckshot Racing #77 Service Tip
Before removing the old filter, note the hose routing and installation direction. Inspect the hoses for hardening, cracking, swelling, oil leakage or loose connections.
On Optimax engines, inspect both inline filters when servicing the compressor system. If a compressor has failed mechanically, do not replace only the compressor without checking the filters and oil-return hoses for debris.
On older EFI or carbureted engines, use the factory diagram to confirm the filter’s exact location and purpose before installation.
The Mercury 8M0207786 filter offered by Buckshot Racing #77 is the current OEM replacement for 8M0042285, 18206001, 18206 and 14991 and fits a broad range of Mercury applications, from classic 100–125 HP four-cylinder engines to 150/175/200 EFI and XRi, Pro Max, and later Optimax, Pro XS, XS, Sport XS, 250XS and 300XS platforms.