A 3" Honda Trash pump will pump at least 300 gallons per minute.
Here's some math that may be helpful.
That pump, even with a 15' head, can move enough water to drop your pond 3 feet in 60 hours.
I rented a 4" pump from a local rental company and dropped my 3/4 acre pond empty in a about 20 hours.
I'd pump it, and get it done.
But, that's me.

Teach a man to grow fish...
He can teach to catch fish...