Piston Kit – Fits Tohatsu/Nissan/Mercury 6HP-9.8HP 2-Stroke (Replaces 3B2-00001-0, 779-804886)

$19.69 $31.00

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Product Details

This aftermarket Piston Kit – Fits Tohatsu/Nissan/Mercury 6HP-9.8HP 2-Stroke is designed for a range of 2-stroke outboard motors. It is a direct-fit replacement for Tohatsu/Nissan 6HP, 8HP, and 9.8HP models (M6B, M8B, M9.8B) from 2002–2003 and later, as well as Mercury 8HP and 9.8HP 2-stroke outboards requiring the specified part numbers.

This kit provides a direct interchange for Tohatsu 3B2-00001-0 / 3B2000010M / 3B2-00001-1, Nissan 3B2-00001-0, Mercury 779-804886 / 803678A3, and Parsun 3B2-00001-0.

Installation: Direct OEM-level replacement fit.
Bore Size: Standard (STD) 50mm bore.
Material: Manufactured from durable aluminum alloy.

Part Number Matrix

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

Brand	Part Number
Tohatsu	3B2-00001-0 / 3B2000010M / 3B2-00001-1 / 3B2000011M
Nissan	3B2-00001-0 / 3B2000010M / 3B2-00001-1 / 3B2000011M
Mercury	779-804886 / 803678A3
Parsun	3B2-00001-0

Engine & Model Compatibility

Confirm your engine model/year in the table below.

Designed for specific Tohatsu M-series and Nissan NS-series 2-stroke outboards.

Also compatible with select Mercury 2-stroke models using the cross-referenced part numbers.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.
Tohatsu	M6B	6	2-Stroke	2002+	3B2-00001-0
Tohatsu	M8B	8	2-Stroke	2002+	3B2-00001-0
Tohatsu	M9.8B	9.8	2-Stroke	2003+	3B2-00001-0
Nissan	NS6B	6	2-Stroke	2002+	3B2-00001-0
Nissan	NS8B	8	2-Stroke	2002+	3B2-00001-0
Nissan	NS9.8B	9.8	2-Stroke	2003+	3B2-00001-0

Technical Specs

Product Type: Piston Kit
Installation: Direct OEM Replacement
Fuel Type: Gasoline (2-Stroke)
Bore: 50mm (Standard Size)
Housing Material: Aluminum Alloy
Product Dimensions: 6.5" x 6.5" x 7.7"
Package Dimensions: 6.5" x 6.5" x 7.7"

What’s in the Box

1 x Piston (3B2-00001-0 / 779-804886)
2 x Piston Rings (3B2-00011-0 / 3B2000110M)
1 x Piston Pin
2 x Circlips

Installation Notes

Ensure the engine is off and cool. Disconnect the battery and spark plug wires for safety.
Remove the engine cowling and any other components obstructing access to the cylinder head.
Carefully remove the cylinder head bolts and head assembly to expose the piston.
Rotate the crankshaft to bring the piston to a workable position.
Remove the old circlips, piston pin, and piston from the connecting rod.
Clean the cylinder bore, piston-ring grooves, and connecting rod of any carbon buildup or debris.
Install the new piston rings on the new piston, ensuring correct orientation.
Lubricate the new piston, rings, pin, and cylinder wall with fresh 2-stroke engine oil.
Install the new piston assembly onto the connecting rod and secure it with the new circlips.
Reassemble the cylinder head using a new gasket, and torque all bolts to the manufacturer’s specifications.
Reinstall all remaining components, reconnect the battery and spark plugs, and check for proper operation.

Troubleshooting & FAQ

How do I know if this piston kit fits my engine?

Check the part number on your old piston or in your service manual. This kit replaces Tohatsu/Nissan 3B2-00001-0 and Mercury 779-804886 / 803678A3. It is confirmed to fit the specific Tohatsu M-series and Nissan NS-series models listed in the compatibility table.

Is this a standard size or oversized piston?

This is a standard (STD) 50mm bore piston kit. It is designed for cylinders that are within original factory specifications and is not an oversized piston for bored-out cylinders.

What are the common signs of a failing piston?

Symptoms of a worn or damaged piston include significant loss of compression, excessive blue or white smoke from the exhaust, a metallic knocking or rattling sound from the engine, and a noticeable decrease in power and performance.

Does this kit require a break-in period after installation?

Yes, a proper engine break-in period is critical. For the first 5–10 hours of operation, vary the engine speed and avoid sustained high-RPM running. This allows the new piston rings to seat correctly against the cylinder wall for optimal compression and longevity.

Is it necessary to replace the whole kit or can I just use the rings?

For a reliable and lasting repair, it is strongly recommended to replace the entire kit—piston, rings, pin, and circlips. Components are designed to wear together, and mixing old and new parts can lead to improper fit, poor sealing, and premature failure.

What's the difference between an OEM part and an aftermarket one?

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.

What are your shipping speed and cost?

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

What is the warranty and return policy?

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

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.

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