By golly More than enough power, (depending on the displacement of the pump). I use a Cessna 20 gpm pump (salvaged off an old Case loader), hooked to a PTO coupler, running at 1000 rpm (pump maximum speed is 1200). I can get cycle times (up and back) of less then 10 seconds, but I usually throttle it down, or run in the 540 rpm setting. Usually I run the Kubota at 2000 rpm and go with the slower cycle times. (Using a 4" cylinder, peaking at 1500psi.)
I once tried (it was a learning experience) splitting gum, or should I say 'splintering' gum. Results were not very pretty, but the power was there.
The advantage of the Kubota is fuel economy. When I used the setup on my Case SC (19 HP) I'd use at least 2 gallons (gas) per hour (usually more). A friend using a B&S 10HP aircooled (very similar setup) is using about 1 gallon of gas per hr. Using the bota, its less than 1/2 gal of diesel per hr.
Steve