Description
The Yanmar 129675-42280 is the genuine OEM V-ribbed drive belt for the Yanmar common rail marine engine range: 3JH40, 4JH45, 4JH57, 4JH80 and 4JH110. On these engines the belt drives the front mounted seawater pump, so it is part of the cooling system as much as the accessory drive.
Carry a spare
This is the single most important spare to have aboard. A V-ribbed belt does not usually fail gradually, and when it goes you lose seawater pump drive, which means you lose engine cooling. That takes a comfortable passage and turns it into an emergency. A spare belt costs a fraction of a cooked impeller, a scorched exhaust elbow, or a tow.
What to look for when you inspect it
Check the belt at every service and before any long trip. Look for cracking across the ribs, glazing on the contact faces, missing chunks of rib material, and black dust building up around the pulleys, which tells you the belt is being chewed. Check the tension while you are there, and check the pulleys themselves for wear and alignment. A belt that keeps failing early is usually telling you a pulley or a bearing is the real problem.
Genuine belt construction
The belt supplied is a genuine Yanmar part manufactured by Mitsuboshi and marked RIB-ACE. Belt compound and rib geometry are what determine how a belt copes with heat, and marine installations run hot in confined engine spaces, so this is not a good place to save money on a pattern part.
Check your fitment
The engine models listed in the product specifications are a guide only. Always confirm against the parts catalogue for your engine’s model and serial number before ordering. If you are unsure, send us your engine plate details and we will check it for you.
Genuine Yanmar parts
We stock genuine Yanmar OEM parts, not pattern copies. If you need help identifying the right part for your engine, or want to book a service, get in touch.
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