Sierra 18-7721 Fuel Filter, Replaces 35-864572, for MPI & EFI Engines with Boost Pump, 8.1L & 496 CID

The Sierra 18-7721 is a replacement fuel filter engineered for MPI and EFI marine engines equipped with a boost pump, specifically 8.1L and 496 cid applications running 3/8 inch ID fuel lines. It is a direct equivalent for the OEM Mercury Marine 35-864572 filter, giving boat owners a straightforward way to restore proper fuel filtration without sourcing the part through the engine manufacturer.

The filter uses a metal outer housing sized at 0.38 inches in diameter and is built to trap contaminants at a 180 micron rating, protecting the fuel injection system and boost pump from debris that can cause clogging, poor performance, or injector wear. Because it is purpose-built for MPI and EFI engines with a boost pump, it is not intended for carbureted fuel systems, which use a different Sierra filter in this catalog family.

Routine replacement of the fuel filter is a standard part of marine engine maintenance, and using a properly rated filter like the 18-7721 helps maintain consistent fuel pressure and delivery. The part is identified by the Sierra part number 18-7721 and is cross-referenced to the OEM Mercury Marine number for buyers who are matching by OEM part number.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-7721
• Product Type: Fuel Filter
• Replaces (OEM): 35-864572
• Fitment: MPI and EFI engines with boost pump, 8.1L and 496 CID, for 3/8 inch ID fuel lines
• Micron Rating: 180
• Outer Material: Metal
• Item Diameter: 0.38 inches
• Weight: 0.32 pounds

Fitment

• MPI and EFI engines with boost pump
• 8.1L and 496 cid engines
• For 3/8 inch ID fuel lines

Replaces (OEM)

• 35-864572

Frequently Asked Questions

What OEM part number does the Sierra 18-7721 fuel filter replace? The Sierra 18-7721 fuel filter replaces Mercury Marine OEM part number 35-864572.

What engines is the 18-7721 fuel filter designed for? It is designed for MPI and EFI marine engines equipped with a boost pump, specifically 8.1L and 496 cid applications.

What fuel line size does the 18-7721 fit? This filter is built for 3/8 inch ID fuel lines.

What is the micron rating of the Sierra 18-7721 fuel filter? The 18-7721 has a 180 micron filtration rating.

What material is the Sierra 18-7721 fuel filter housing made of? The outer housing of the 18-7721 fuel filter is metal.

How much does the Sierra 18-7721 fuel filter weigh? The 18-7721 weighs 0.32 pounds.

What is the diameter of the Sierra 18-7721 fuel filter? The 18-7721 has an item diameter of 0.38 inches.

Will the 18-7721 work on a carbureted engine? No, the Sierra 18-7721 is built specifically for MPI and EFI engines with a boost pump, not carbureted fuel systems.

Is the Sierra 18-7721 a genuine Sierra part? Yes, 18-7721 is the Sierra part number for this fuel filter, sold as a Sierra-branded replacement for the Mercury Marine 35-864572.

Is the Sierra 18-7721 fuel filter a universal fit? It fits any MPI or EFI engine with a boost pump that uses 8.1L or 496 cid displacement and 3/8 inch ID fuel lines, rather than being limited to a single boat make or model.

How do I know if the 18-7721 is the correct fuel filter for my engine? Confirm your engine is an MPI or EFI type with a boost pump in the 8.1L or 496 cid range using 3/8 inch ID fuel lines, or match against OEM number 35-864572, before ordering the Sierra 18-7721.