Description

Yanmar 119578-18420 is an O-ring seal used in select Yanmar marine diesel applications. Public parts references most consistently place this part in intercooler / air-cooler / intake-manifold sealing applications, with the strongest fitment trail pointing to 6LY3-series engines and some related 6CX-series applications. The available public data supports this as a model-specific sealing ring rather than a universal O-ring.

Key Features

• Yanmar part number 119578-18420
• Identified in public listings as O-RING or O-RING SEAL
• Commonly associated with intercooler / air cooler / intake manifold sealing locations
• Found in public Yanmar catalog references for multiple 6LY3-series engine variants
• Also appears in some public references tied to certain 6CX-series applications
• Best matched by exact part number and engine application rather than by dimensions alone

Engine Compatibility
Available public references most clearly associate Yanmar 119578-18420 with 6LY3-ETP, 6LY3-STC, 6LY3-STP, 6LY3-UTC, and 6LY3-UTP applications, and Yanmar catalog results also show it in certain 6CX engine schematics. Some aftermarket listings describe broader compatibility such as 6LY2A, 6LY, and 6CX families. Because the public fitment trail spans multiple variants and sources use slightly different naming, this should be treated as a serial-number-confirmed sealing part.

Serial Number Fitment Notice
Please confirm fitment by full engine model and serial number before ordering. This is especially important because the same part number appears across multiple intercooler or intake-related schematic contexts, and public descriptions are brief.

When This Part Needs Replacement
Replace this O-ring whenever the related intercooler, air-cooler, or intake-manifold cover is removed and the seal is flattened, hardened, torn, swollen, leaking, or no longer sealing correctly. Public sources identify the part and application context, but detailed service-interval guidance is naturally limited, so this replacement guidance is based on its sealing function.

Installation Notes
Install only on the correct Yanmar application and confirm the exact sealing location before ordering. Because public sources place this part in intercooler / intake-manifold assemblies, matching by part number, engine model, serial number, and removed seal location is the safest approach.

Alternate / Superseded Part Numbers

• 119578-18420
• Public service-kit listings also show this exact number as O-RING SEAL within onboard spares kits for applicable Yanmar engines

Parts Desk Insight
This is the kind of Yanmar sealing part where the public data is useful but naturally limited. The strongest evidence says it belongs in an intercooler / air-cooler / intake-manifold sealing position, but the safest sale is still against the exact engine model and serial number, especially on 6LY and 6CX applications where assemblies can vary.

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