Water pump shaft repair (?)

When I stripped the block to be bored out for oversize pistons I found my water pump impeller had worn again and the lobes on the pump shaft were rusting away. This meant there wasn't enough key left to prevent me turning the impeller on the shaft by hand!

The last time I had the engine out I put a new impeller in (they were still available then) because the original had rounded off it's keyway.

This is what the key on the shaft looked like:

I bought a brand new after market CNC machined impeller from MCG but I couldn't afford their pump shaft as well.

My idea was to build up the lobes on the shaft with a MIG welder and get a friend to turn the weld back on his lathe. My 90 amp MIG wasn't laying down much metal so my friend did the MIG welding too with his 160 amp machine. This is the "repaired" shaft:

And located in the impeller (without the ceramic seal):

These are the components ready to go back in:

That ceramic seal is part of a brand new mechanical seal. It has only had about an hour running at idle before I stripped the block again.

Seems like a reasonable fix - the end of the shaft being in the coolant constantly certainly the weakest part of the cooling system. The radiators seem to last forever.