Leave it with me and I will have a look at the spec.
It came off the 24 HP engine and there seemed to be a massive differential between the engine & the pump, to the point that we were going to put a 45LPM pump onto the engine in it's place. If we didn't need to have a small amount for the burner I would have gone for it and even now I still think that the engine would handle the pump and the burner.
The service people said I needed to have 1 or 2 Hp for the burner
General Pump are owned by Interpump.
You will run a 21LPM off a 13Hp so I guess this would run the same. Not technical though but I am sure Chris or Carl will know
Rob