Head Gasket – Fits Johnson/Evinrude 2-Cylinder 20-35 HP Outboards (Replaces 329419, 765012, 777390)

Product Details

This replacement Head Gasket fits Johnson/Evinrude 2-Cylinder 20-35 HP Outboards, including 20, 25, 28, 30, and 35 HP models manufactured between 1984 and 2004. It ensures a secure seal between the cylinder head and the engine block.

This part is a direct interchange for Johnson/Evinrude part numbers 329419, 765012, and 777390, as well as Sierra 18-3803, GLM 34570, and ProPart 329419.

• Engineered for direct OEM-spec replacement and straightforward installation.
• Made from durable composite material for a reliable, long-lasting seal in marine environments.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Evinrude motors, this gasket fits a wide range of 20, 25, 28, 30, and 35 HP 2-stroke models from 1984 to 1987. Please verify your specific model code from the list.

This part is compatible with Johnson 20, 25, 28, 30, and 35 HP 2-stroke outboard engines manufactured between 1984 and 2004. As specific model codes are not listed, please verify fitment based on your engine's horsepower and year.

Technical Specs

Product Type

Cylinder Head Gasket

Installation

Direct OEM Replacement

Fuel Type

Gasoline

Housing Material

Composite

Dimensions

22.5" L x 15.5" W x 1.0" H

Other Technical Attributes

For 2-cylinder outboard motors

What’s in the Box

• 1 x Cylinder Head Gasket (329419/765012/777390)

Installation Notes

1. Ensure the engine is off and cool, and disconnect the battery terminals.
2. Remove the engine cover and any components blocking access to the cylinder head.
3. Carefully disconnect spark plug wires. Loosen and remove the cylinder head bolts in the reverse order of the tightening sequence specified in your service manual.
4. Gently lift the cylinder head away from the block. If it sticks, do not pry; tap it with a rubber mallet.
5. Remove the old head gasket. Thoroughly clean the mating surfaces of both the cylinder head and engine block, ensuring they are free of any old gasket material, sealant, or debris.
6. Position the new gasket on the engine block, ensuring it aligns correctly with dowel pins and bolt holes. Do not use sealant unless explicitly required by the manufacturer.
7. Carefully place the cylinder head back onto the block and install the head bolts.
8. Tighten the bolts to the manufacturer’s specified torque in the correct sequence using a torque wrench.
9. Reconnect spark plug wires and all other components. Reconnect the battery.
10. Check for any leaks and ensure proper engine operation before taking your boat on the water.

Troubleshooting & FAQ

Safety & Important Info

• Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
• This is an aftermarket replacement, not an OEM component.
• Professional installation is recommended for safety and performance.

About Sea Sierra

• Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
• Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
• Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.