Piston Ring Kit – Fits Yanmar Diesel Engines (Replaces 721000-22500)

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Product Details

This aftermarket Piston Ring Kit is engineered for a precise fit in various small to medium-sized Yanmar marine diesel engines. It serves as a direct-fit component, designed to restore the crucial seal between the piston and the cylinder wall, ensuring optimal compression and engine performance.

This kit is a direct replacement for Yanmar OEM part number 721000-22500.

Installation Method: Direct OEM Replacement
Primary Function: Provides a dynamic seal between the piston and cylinder wall
Engine Fuel Type: Diesel

Part Number Matrix

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

Brand	Part Number
Yanmar	721000-22500

Engine & Model Compatibility

Confirm your engine model/year in the table below.

Information on specific compatible engine models is limited. This part is confirmed as a direct replacement for OEM part number 721000-22500, which is used across various Yanmar diesel engines. Always verify fitment by comparing your old part's specifications and number.

Technical Specs

Product Type: Piston Ring Kit
Installation: Direct OEM Replacement
Fuel Type: Diesel
Dimensions: L 12.0 x W 11.0 x H 0.8 inches
Other Technical Attributes: Provides seal between piston and cylinder wall

Installation Notes

Ensure the engine is cool and disconnect the battery.
Drain the engine oil and coolant completely.
Remove the cylinder head and any other components obstructing access to the pistons.
Carefully extract the piston from the cylinder bore.
Use a designated ring expander tool to safely remove the old piston rings.
Thoroughly clean the piston, ensuring the ring grooves are free of carbon buildup and debris.
Install the new rings onto the piston using the expander, verifying correct sequence and orientation per the engine manual.
Check ring end gaps and stagger them around the piston according to manufacturer specifications.
Liberally lubricate the new rings, piston, and cylinder wall with fresh engine oil.
Use a piston ring compressor to gently guide the piston and ring assembly back into the cylinder.
Reassemble all engine components in reverse order, torquing all bolts to the manufacturer's specified values.
Refill the engine with the correct type and amount of oil and coolant before starting.

Troubleshooting & FAQ

How do I know if my piston rings need replacing?

Common signs of worn or failing piston rings include a noticeable increase in oil consumption, blue or white smoke from the exhaust, a measurable loss of engine power, and poor results from a compression test.

Is this kit for a single piston or a full engine set?

This kit contains the rings for one piston. Please verify the total number of pistons in your engine and purchase the appropriate number of kits for a complete engine overhaul.

Do these rings require a specific break-in procedure?

Yes, a gentle break-in period is recommended. After installation, avoid operating the engine at high RPMs or under heavy loads for the first few hours. This allows the new rings to seat correctly against the cylinder wall for optimal performance and longevity.

What is the primary function of piston rings?

Piston rings serve three critical functions: sealing the combustion chamber to maintain compression, transferring heat from the piston to the cylinder wall, and regulating the flow of oil to lubricate the cylinder.

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

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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