One of the basic rules of thumb, for hydraulics:
http://www.metaris.com/hp-calculator.php
According to that, your Honda motor - with the adequate pump and working at 3000psi, should be able to produce almost 13 GPM.
For reference, the chart below shows the pump specs for the various HEMTT "Material Handling Cranes"...
Your crane may be comparable to the higher cap. M978 and M984 models, and the max. working pressure should be the same for all of them.
Maybe a bit slow, but it will work.