For a 2.5 inch water pump, it depends on your lift height and the power of your water pump. If you do not use soft start, the generator power is usually three times that of the water pump. , which means that the power of the water pump should be 6.5 /3 = approximately 2.2 kW.
In addition, if you pump water frequently, it is estimated that your gasoline cost will be very high. You can consider others. methods, such as photovoltaic solar water pumps,