Holding a gear to lock a shaft.

[jimmer2880]

Have you tried a strap wrench, something like this:

Harbor Freight Tools - Quality Tools at the Lowest Prices

They are rubber & plastic. I have a pair from Harbor Freight. Not the best quality, but I have put a TON of torque on them and not broken them yet.

 

[hbaird]

Thanks for all the suggestions. The vendor now says the pump is not repairable and is replacing it under warranty.
Harold