I second Rich's comment.. It would be strange to have a pump failure without spraying coolant all over! Loosen the belt and try to wobble the shaft.. IF the shaft wobbles, a new pump will be required:
Category:Engine Parts & Accessories > Yanmar Engines and Parts
Manufacturer: Yanmar
Part Number: 121000-42100
Description:
Cooling Fresh Water Pump Body Assembly
Part #121000-42100 from Yanmar
Note: Does not include mounting gasket 121000-42051
Our price: $144.45 - each
If only the pulley wobbles, check the mounting holes for cracks .. you may be able to simply tighten it.. or if you need a new pulley, it is :
Category:Engine Parts & Accessories > Yanmar Engines and Parts
Manufacturer: Yanmar
Part Number: 128695-42350
Description:
Fresh water pump V pulley
Part #128695-42350 from Yanmar
Our price: $22.35 - each
These from Toad Marine, your area's distributor.
http://shop.toadmarinesupply.com/marine_diesel_direct/Yanmar/