Originally Posted by bus-bro
If you're using a jet pump that would mean you are trying to lift water at 20 plus foot elevation. If you put a portable pump closer to the source of water you could use a pump that would draw less current than a jet pump. Then you'd need to size the power cord to the pump. It then becomes more of a question of how much water you want to lift in a given time, and, of course, the total lift.
to move water, it is very very difficult to suck or pull water over a long distance or elevation. As a matter of fact, it is impossible to pull water much over 25 feet elevation.
It is much easier and more efficient to pump or push water. Get a pump you can put near the water source and pump it to the bus. Either 12 volt, 110 volt or an actual gasoline powered pump.
If you want to use your bus engine to pump water, you need attach a pump to the bus engine (think firetruck) But this pump needs to only turn when you want to move water. It cannot spin when there is no water or you will burn it up. But for this to work, you need to park near the water source. Many pumps are not rated for any sort of side loading, so you cannot simply run it off a belt, but requires a drive shaft or similar setup.
The simplest solution is either a larger inverter to run your existing pump, or a smaller pump. 110 volts through your inverter has the advantage that if you are going to run the pump any distance away from the bus you can use an extension cord. You need to carry 10 times the current to run a similar size pump at 12 volts which makes it not practical at any distance because of the size conductors required.
depending on how many gallons per minute you require a small 12 volt pump and a spare bus battery near the water source may be a good solution.
as far as engine powered generator, there are commercial engine driven generators that are hydraulic drive. Your engine turns a hydraulic pump that spins a hydraulic motor that spins a generator head. I imagine these start at about $10K These allow for varying engine speed while keeping volts and hz relatively constant.
One thing i've thought would be fun to play with is a honda inverter type generator coupled to a bus engine. Most generators require constant rpm to make the proper output 110 volts and 60 hz. The honda eu series are different as they make 110 volts and 60 hz at various speeds. (they are actually a complex alternator and an inverter) If only you could find a cheap honda with a damaged motor you could modify to spin off the bus engine with a belt. Then you could make pure 60 hz power at any speed.