Description

The Yanmar 129673-44131 is a genuine OEM coolant filler cap used on select Yanmar marine diesel cooling systems. Current Yanmar catalog references identify this part as CAP, FILLER, and dealer listings place it in the fresh-water cooling / coolant tank assembly.

Current fitment support confirms this cap on multiple Yanmar marine engine families, including 2YM, 3YM, 3JH, and 4JH applications. Reviewed sources specifically list fitment for engines such as 2YM15, 3YM20, 3YM30, 3YM30AE, 3JH4, 3JH5, 3JH40, 4JH3, 4JH4, 4JH5, 4JH45, 4JH80, and 4JH110, depending on model and production range.

Key Features
Genuine Yanmar OEM coolant filler cap.
OEM part number: 129673-44131.
Current Yanmar description: CAP, FILLER.
Used in fresh-water cooling / heat exchanger / coolant tank applications on supported engines.

Engine Compatibility
Current supported references associate 129673-44131 with select Yanmar marine engines in the 2YM, 3YM, 3JH, and 4JH families. Supported examples include 2YM15, 3YM20, 3YM30, 3YM30AE, 3JH4, 3JH5, 3JH40, 4JH3-DTE, 4JH3-HTE, 4JH4(A)E, 4JH4E, 4JH5E, 4JH45, 4JH80, and 4JH110. Fitment should still be confirmed by exact engine model and serial number before ordering.

Serial Number Fitment Notice
Fitment should be verified by engine model and serial number before ordering. Matching by OEM part number 129673-44131 remains the safest method.

When This Part Needs Replacement
Replace the cap if the seal is damaged, pressure retention is reduced, corrosion is present, or the cap no longer fits securely. A worn coolant cap can affect proper cooling-system pressure and make leak diagnosis more difficult. This service guidance is based on the function of a coolant filler cap; the reviewed sources mainly confirm part identity and fitment.

Installation Notes
Install only where 129673-44131 is specified. Confirm the existing cap and filler-neck application match before installation. Reviewed sources also describe this part as a heat exchanger / fresh-water cooling cap, which helps confirm the intended service location.

Alternate / Superseded Part Numbers when applicable
No superseded OEM number was confirmed in the reviewed sources. The supported OEM part number is 129673-44131.

Parts Desk Insight
This is a small part, but it plays an important role in the cooling system. On Yanmar fresh-water-cooled engines, a tired filler cap can create nuisance cooling issues that look bigger than they are, so replacing a weak cap is often a smart preventative-maintenance step.

Shipping
Shipping: Ships same or next day for fast Canada wide shipping.