Coolant leak 450 fe 09

Sounds like you are describing a common leak from the "weep" hole. Search the forum for some of the ways this is addressed and fortified. Dust and debris can potentially get down the hole and cause premature wear on the shaft and seal. More common is that the factory water pump seal was installed BACKWARDS and allows coolant to escape under pressure. Even the service manual that you can access from this site shows the seal installed backwards. The outer seal that is in direct contact with the coolant, behind the water pump rotor, should have the spring-loaded side visible and facing outward. I drilled a tiny hole in each seal cover to insert a point and pry out. Threading in a small wood screw will also work. Be mindful of any chips you may create when dealing with the second seal and use a magnet. Below are the OEM parts ordered from RMATV. $10 x 2 for seals, and a $5 gasket. I also replaced the plastic pump disks for good measure. MIne is a 10' FE450 (3rd owner) and the seal was backwards.

Picture is of the outer seal properly seated, spring lip outward...

https://www.rockymountainatvmc.com/oem-schematic/13

WATER PUMP COVER GASKET 187866000020 $5.31 2 $10.62
SHAFT SEAL RING 10X24X4 131307000216 $10.06 1 $10.06
SHAFT SEAL RING 10X24X5,5 131307000217 $9.14 1 $9.14
DISC WATER PUMP 131307004029 $2.93 1 $2.93
WATER PUMP ROTOR 131307004025 $6.92 1 $6.92