Sierra 18-3899 Water Cover Gasket for Johnson/Evinrude 20, 25, 25C, 30, 35 HP Outboards

The Sierra 18-3899 Water Cover Gasket is a round gasket engineered to seal the water cover on Johnson/Evinrude outboard motors rated 20, 25, 25C, 30, and 35 HP. It creates a reliable seal between the water cover and powerhead, helping maintain proper cooling system integrity and preventing water intrusion or leaks at the cover joint. As a Sierra Marine product, it is built to meet or exceed the specifications of the original equipment part it replaces, giving boat owners a dependable option when servicing the outboard's cooling passages during a rebuild or routine maintenance.

This is a single-piece gasket (one gasket per package) intended for direct fitment on the applicable Johnson/Evinrude horsepower range. Sierra supplies OEM engine manufacturers and boat builders with quality parts daily, and every Sierra part is backed by Sierra's customer satisfaction warranty.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3899
• Product Name: Water Cover Gasket
• Shape: Round
• Unit Count: 1 gasket
• Weight: 0.04 pounds
• UPC: 808282244118

Fitment

• Johnson/Evinrude outboards: 20, 25, 25C, 30, 35 HP

Frequently Asked Questions

What is the Sierra 18-3899 gasket used for? The Sierra 18-3899 is a water cover gasket that seals the water cover on Johnson/Evinrude outboard motors, helping maintain a proper seal in the cooling system.

Which outboard motors does the 18-3899 gasket fit? It fits Johnson/Evinrude outboards rated 20, 25, 25C, 30, and 35 HP.

How many gaskets come in one package? Each package of part number 18-3899 contains one water cover gasket.

What shape is the 18-3899 water cover gasket? The gasket is round in shape, matching the water cover it is designed to seal.

How much does the 18-3899 gasket weigh? The Sierra 18-3899 water cover gasket weighs 0.04 pounds.

Is the Sierra 18-3899 an OEM or aftermarket part? It is a Sierra aftermarket part engineered to meet or exceed the specifications of the original equipment water cover gasket it replaces.

Does the 18-3899 gasket come with a warranty? Yes, the 18-3899 is covered under Sierra's customer satisfaction warranty like all Sierra parts.

When would I need to replace this water cover gasket? This gasket should be replaced any time the water cover is removed for service or if the existing gasket shows signs of leaking or deterioration on a Johnson/Evinrude 20-35 HP outboard.

What is the UPC for the Sierra 18-3899 gasket? The UPC for the Sierra 18-3899 water cover gasket is 808282244118.

Is the 18-3899 gasket compatible with the 25C model specifically? Yes, the 25C horsepower variant is included in the listed fitment for the Sierra 18-3899 water cover gasket, along with the 20, 25, 30, and 35 HP models.