Cavin, post a photo of the gauges and describe what function you think each one performs. Seeing a photo of the gauges someone here will be able to tell you what they all mean. There is no such thing as a water pressure gauge AFAIK.
The Gauges
Good thing I'm a night-owl. Or an insomniac, one of the two.
Nige: first of all, I was thrilled to see you had posted to this thread! I read your posts with great interest as your knowledge of heavy equipment is encyclopedic. You had me questioning what I had seen and I didn't want to address the gauges until I could double check things and take some photos. So, here they are:
Clockwise, from upper right, the gauges are ammeter, fuel pressure, engine oil pressure, water temperature, water pressure, and converter temp (F). The two knobs: left is the preheat/start and right is the lights (most of which work, amazingly!).
The left cluster in more detail:
The upper left gauge is the torque converter temperature. Why it is labeled as "TEMP F" is beyond me as it is a qualitative gauge (it has no numbers), so why specify Fahrenheit? It could be in Kelvins or yo-yo degrees.... Anyhow, this gauge doesn't seem to work as it hasn't moved a bit. But it could also be that I haven't worked it enough to make it move!
Below the converter temp is the more interesting water pressure gauge. The colors are faded, but the bottom segment is green, the middle is blue, and the top right is yellow. To the right of that gauge is the water temperature gauge. Again, it is faded--the bottom portion is green/red, the middle blue/red, and the top yellow/red. The quotes by Delmer (post #16 herein) are right on. Specifically, the row in the water temperature gauge corresponds to what color the water pressure gauge is pointing to. The higher the pressure, the higher the temp can be without boiling. Personally, I think that is a great combination to have! It tells you a lot about what is going on in the cooling system. Today (er, yesterday), I ran the rattletrap for about a half-hour (all I had time for) a good portion of which was at or near full-throttle. I did some pushing, dropped a couple of trees, and otherwise just played around getting used to the machine. The water pressure gauge never moved out of the green zone and the water temperature gauge barely budged. After I parked it (running it at an idle for about 5 minutes in the process) and with it running I opened the engine hatch to see if it felt hot to double check if the temp gauge was accurate. It didn't seem to be hot at all. I checked the radiator hatch. The radiator was cool enough that I could lay my hand on the tank! If anything, it is running too cold. I'm wondering if the previous owner removed the thermostats (can't find that info in the manuals I have--might have to dig some more). Anyhow, until an issue presents itself, I'm not concerned about the cooling system.
Regarding the other gauges: the engine oil pressure jumps immediately into the green and stays there. The ammeter gauge works as it should and the batteries are doing their job (thankfully!). But the fuel pressure gauge is in the yellow unless it is at full-throttle at which point it is at the very bottom of the green. As there doesn't seem to be a loss of power (at least not that I can tell!), I'm not going to sweat that, either.