Yanmar 721575-42502 Pump Shaft for GM and GMF
The Yanmar 721575-42502 is the factory pump shaft used in the bronze sea water pump fitted to GM and GMF Series engines. It does two jobs at once: transmitting torque to the impeller and providing a ground, true running surface for the seals around it.
Corrosion is the marine version of the same problem. Salt water that has been past a failed seal pits the shaft along its length, and a pitted shaft destroys new seals as fast as they are fitted. The keyway or drive flats are the third area to check, because a worn drive lets the impeller move on the shaft and that movement shows up as uneven vane wear.
Key Features
- Genuine Yanmar replacement pump shaft
- Fits the bronze sea water pump fitted to GM and GMF Series engines
- One per pump
- Ground sealing surface for correct seal life
- Carries the drive from the engine into the impeller
- Renew the pump seals at the same time
Applications
- the bronze sea water pump fitted to GM and GMF Series engines
- Raw water pump rebuilds
- Replacing a shaft grooved where the seal runs
- Repairing corrosion after salt water past a failed seal
- Restoring a worn impeller drive
- Spring commissioning and layup service
Specifications
- Brand: Yanmar
- Manufacturer: Yanmar Marine
- Manufacturer Part Number: 721575-42502
- Part Type: Pump Shaft
- Fits: The bronze sea water pump fitted to GM and GMF Series engines
- Quantity Used: One per pump
- Condition: New
Frequently Asked Questions
Q: Can I sleeve or polish a grooved shaft?
Polishing removes material and moves the sealing diameter, which is not what you want on a part this size. Replacement is the reliable answer.
Q: Should I replace the bearing at the same time?
Check it. A shaft that has worn unevenly usually did so because the bearing allowed movement, and fitting a new shaft into a tired bearing repeats the wear.
Q: Why does the shaft corrode?
Salt water that has been past a failed seal sits against it. That is why a weeping seal is worth dealing with early rather than at the next service.
Q: Does the impeller drive matter?
Very much. A worn keyway or drive flat lets the impeller move on the shaft, which wears the vanes unevenly and eventually rounds off the drive altogether.
Not sure this is the right part? Send us a Picture of the Pump Plate on your pump and the CLR Marine team will confirm the correct pump shaft.
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