Piston Kit, 0.030 Oversize – Fits Johnson/Evinrude 20-35 HP 2-Cylinder (Replaces 5006664)

$119.95 $191.00

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Product Details

This Piston Kit, 0.030 Oversize, is designed for Johnson/Evinrude 2-cylinder crossflow engines, including 20 HP (1981–1983), 25 HP (1986–1994), 30 HP (1984–1994), and 35 HP (1981–1994) models. It's engineered as a high-quality replacement for cylinders that have been machined 0.030" over the standard bore size.

This kit serves as a direct replacement for Johnson/Evinrude part numbers 5006664 and 778468, and interchanges with Mallory Marine 9-53414, GLM 23930, and Wiseco 3127P3/3027P3.

Designed for engine internal installation.
Complete kit includes piston, rings, wrist pin, and retainers.
For use in gasoline-powered 2-stroke marine engines.

Part Number Matrix

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

Brand	Part Number	Notes
Johnson/Evinrude	5006664 / 778468	Supersedes 396576, 396379, 320954, 317831
Mallory Marine	9-53414	Aftermarket equivalent
GLM	23930	Aftermarket equivalent
Wiseco	3127P3 / 3027P3	Aftermarket equivalent

Engine & Model Compatibility

Confirm your engine model/year in the table below.

This piston kit is specifically for the following Johnson/Evinrude models. Ensure your cylinder has been bored to the correct oversize dimension before ordering.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Johnson/Evinrude	2-Cylinder Crossflow	20	2-Stroke	1981–1983	5006664/778468	Replaces 396576, 396379, 320954, 317831
Johnson/Evinrude	2-Cylinder Crossflow	25	2-Stroke	1986–1994	5006664/778468	Replaces 396576, 396379, 320954, 317831
Johnson/Evinrude	2-Cylinder Crossflow	30	2-Stroke	1984–1994	5006664/778468	Replaces 396576, 396379, 320954, 317831
Johnson/Evinrude	2-Cylinder Crossflow	35	2-Stroke	1981–1994	5006664/778468	Replaces 396576, 396379, 320954, 317831

Technical Specs

Product Type: Piston Kit, 0.030" Oversize
Installation: Engine Internal Component
Fuel Type: Gasoline
Housing Material: Aluminum Alloy
Dimensions: 3.030" (76.96 mm) Diameter [+0.030" oversize from standard 3.000"]
Other Technical Attributes: Includes rings, wrist pin, and retainers

What’s in the Box

1 x Piston Kit (Replaces 5006664) - SOLD INDIVIDUALLY
Includes: Piston, Rings, Wrist Pin, and Retainers

Installation Notes

Ensure the engine is off, cool, and disconnected from the battery and fuel source.
Drain the engine oil and coolant.
Remove the cylinder head and any components obstructing access to the pistons.
Carefully extract the old piston, wrist pin, and retainers from the connecting rod.
Before installation, verify the cylinder has been bored to the correct 0.030" oversize dimension (3.030").
Install the new rings onto the new piston according to the ring manufacturer's gap and orientation guidelines.
Lubricate the piston, rings, and cylinder wall with fresh engine oil.
Install the new wrist pin and retainers to connect the piston to the connecting rod.
Use a piston ring compressor to carefully guide the piston assembly into the cylinder.
Reassemble the engine in reverse order, torquing all fasteners to the manufacturer's specifications.
Refill with fresh oil and coolant.
Follow a proper engine break-in procedure to allow the new rings to seat correctly.

Troubleshooting & FAQ

How do I know if I need an oversize piston?

An oversize piston is required when a cylinder is machined (bored) to correct for wear, tapering, or scoring. If your cylinder has been bored to 3.030 inches, this +0.030" piston is the correct size. Always measure the cylinder bore with a precise tool before ordering.

Will this piston fit a standard, non-bored cylinder?

No. This is an oversize piston and will not fit in a standard 3.000" cylinder bore. Attempting to install it will cause severe engine damage. You must use a standard-size piston for a non-bored cylinder.

What are the signs of a worn or failed piston?

Symptoms of a failing piston or piston rings include a noticeable loss of compression and power, excessive blue or white smoke from the exhaust, increased oil consumption, and a distinct knocking or rattling sound from the engine.

Does this kit contain parts for one or two cylinders?

This kit services a single cylinder. It includes one piston, one wrist pin, two retainers, and a complete set of rings for the one piston. If you are rebuilding both cylinders of your 2-cylinder engine, you will need to purchase two kits.

What is the correct break-in procedure for this piston?

Always follow the engine manufacturer’s break-in procedure. A general guideline is to run the engine at varied, moderate RPMs for the first few hours of operation, avoiding sustained high speeds or heavy loads. This allows the new piston rings to seat properly against the cylinder wall.

Is any special tooling required for installation?

Yes, professional tools such as a piston ring expander, a ring compressor, and a torque wrench are essential for proper and safe installation. Access to a cylinder bore gauge is also necessary to confirm dimensions.

OEM vs. Aftermarket?

This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.

Shipping speed & cost

We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.

Warranty & returns

Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.

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

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