Sierra 18-2864-9 Powerhead Base Gasket, Replaces 321727, Fits Johnson/Evinrude V-4 25/35 HP Outboards, Pack of 2

The Sierra 18-2864-9 is a powerhead base gasket sold as a pack of two, designed to seal the base of the powerhead on Johnson and Evinrude V-4 outboard engines rated 25/35 HP. This gasket sits between the powerhead and the engine block, forming the critical seal that keeps combustion pressure, oil, and coolant properly contained during operation. A worn, cracked, or compressed base gasket is a common source of oil seepage, loss of compression, or overheating on these outboards, and replacing it with the correct Sierra part restores the factory seal.

Sierra manufactures this gasket to meet or exceed the specifications of the original equipment part it replaces, giving it a reliable fit and consistent sealing performance without modification to surrounding components. Because it ships two to a package, buyers performing a full powerhead service have enough material on hand without needing a second order, and the pack covers engines that use two gaskets per rebuild or a spare for a future service.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-2864-9
• Product Type: Powerhead Base Gasket
• Package Quantity: 2 gaskets per pack
• Fits: Johnson/Evinrude V-4 outboards, 25/35 HP
• Weight: 0.12 pounds
• Replaces (OEM): 321727

Fitment

• Johnson/Evinrude V-4 outboards, 25/35 HP

Replaces (OEM)

• 321727

Frequently Asked Questions

What engines does the Sierra 18-2864-9 powerhead base gasket fit? This gasket fits Johnson and Evinrude V-4 outboard engines rated 25/35 HP.

How many gaskets come in a pack? The 18-2864-9 is sold as a pack of two powerhead base gaskets.

Does the 18-2864-9 replace an OEM Johnson/Evinrude part number? Yes, it replaces OEM part number 321727.

Is the Sierra 18-2864-9 gasket genuine OEM or aftermarket? It is an aftermarket Sierra replacement gasket, manufactured to meet or exceed the specifications of the original equipment part it replaces.

How much does the powerhead base gasket weigh? The 18-2864-9 pack weighs 0.12 pounds.

What is a powerhead base gasket used for? A powerhead base gasket seals the joint between the outboard powerhead and the engine block, containing combustion pressure, oil, and coolant so the engine runs without leaks or loss of compression.

Will I need one or two of these gaskets for a single engine rebuild? Since the 18-2864-9 ships two per pack, one package supplies both gaskets typically needed for a Johnson/Evinrude V-4 powerhead service.

What signs indicate the powerhead base gasket needs replacing? Oil seepage at the base of the powerhead, loss of compression, or overheating on a Johnson/Evinrude V-4 25/35 HP outboard are common signs the 18-2864-9 gasket needs replacement.

Is installation of the 18-2864-9 gasket something a DIY mechanic can do? Replacing a powerhead base gasket requires removing the powerhead from the engine block, so it is a more involved job typically done during a full teardown or rebuild rather than a quick DIY swap.

Does the Sierra 18-2864-9 come with a warranty? Yes, this Sierra powerhead base gasket is covered under Sierra's standard customer satisfaction warranty.