Sierra Marine Fuel/Water Separating Filter 18-7846

The Sierra Marine 18-7846 Fuel Water Separating Filter, also cross-referenced as Aqua Power AP-6040, is a marine spin-on replacement filter designed for compatible fuel/water separator heads. It helps protect outboard, inboard, and sterndrive fuel systems by separating water and capturing sediment before fuel reaches the engine.

This filter is commonly used in OMC, Johnson, Evinrude, Crusader, Quicksilver, Mallory, and GLM cross-reference applications where the fuel system calls for Sierra 18-7846, AP-6040, or a verified equivalent.

Key Features

• Marine spin-on fuel/water separating replacement filter.
• Sierra Marine part number: 18-7846.
• Aqua Power cross-reference: AP-6040.
• Designed for compatible marine fuel/water separator filter heads.
• Helps separate water from gasoline before it reaches the engine.
• Helps capture sediment and fuel-system debris.
• Typical filtration rating: 21 micron.
• Flow reference: up to 90 GPH where the fuel system and filter head support that rating.
• Thread reference: 1 in.-12.
• Approximate canister height: 4.3 in.
• Built for marine fuel-system service in damp bilge and engine-room environments.
• Suitable for compatible ethanol-blended marine gasoline applications.
• Designed not to separate 2-cycle oil from gasoline mixes when used in the correct application.

Fuel System Compatibility

Common application context includes compatible marine fuel/water separator systems used with:

• OMC fuel system applications where listed.
• Johnson and Evinrude outboard fuel systems where listed.
• High-horsepower outboard engines.
• Marine inboard gasoline engines.
• Sterndrive fuel systems.
• Commercial and recreational vessel fuel systems.
• Filter heads requiring a 1 in.-12 threaded replacement filter.
• Applications that call for Sierra 18-7846, Aqua Power AP-6040, or a verified equivalent.

Use this filter only where the filter head, thread size, gasket fit, fuel type, flow requirement, and engine service information confirm compatibility.

Fitment Notice

Confirm fitment by matching the existing filter number, filter head thread, gasket diameter, canister clearance, fuel type, and required fuel-flow capacity before ordering. Marine fuel/water separating filters can look similar but differ in thread size, gasket fit, canister height, micron rating, and flow capacity.

This is a replacement spin-on filter only. It does not include the filter head, mounting bracket, fittings, fuel hose, primer components, or complete separator assembly.

When This Part Needs Replacement

Replace the fuel/water separating filter during routine seasonal fuel-system service, after contaminated fuel exposure, after water is found in the fuel system, or when the engine shows signs of fuel restriction such as hard starting, rough idle, hesitation, surging, loss of power, or stalling under load.

Replacement is also recommended if the filter canister is rusted, dented, leaking, clogged, or past the service interval recommended for the engine and fuel system.

Installation Notes

Shut off the fuel supply before servicing the fuel/water separator. Place absorbent material under the filter, remove the old filter, and confirm the old gasket is not stuck to the filter head. Clean the sealing surface before installation.

Lightly lubricate the new gasket with clean fuel or engine oil, install the filter by hand, and tighten according to the filter head or engine service instructions. Do not over-tighten. After installation, prime the fuel system, check carefully for leaks, and run the engine while inspecting all fuel connections.

Dispose of the used filter and any contaminated fuel according to local environmental requirements.

Alternate / Cross-Reference Part Numbers

• Sierra Marine 18-7846 primary part number
• Aqua Power AP-6040 cross-reference reference
• OMC / Johnson / Evinrude 502905 cross-reference reference; verify by application
• Crusader 98041 cross-reference reference; verify by application
• Quicksilver 8M0061975 cross-reference reference; verify by engine serial number
• Mallory Marine 9-37803 cross-reference reference; verify by application
• GLM 24930 cross-reference reference; verify by application

Parts Desk Insight

The key checks on this filter are the 1 in.-12 thread, gasket fit, canister clearance, and fuel-flow requirement. A correct fuel/water separating filter protects the engine only when it seals properly to the existing filter head and is replaced before contamination or restriction affects fuel delivery.

Shipping: Ships same or next day for fast Canada wide shipping.