Like Racer said, its for monitoring engine block water temperature or pressure. Some folks like pressure monitoring as an aid to keep tabs on how well the impeller is working, especially for long trips. I use it for temperature monitoring as that is what interests me. Since you have no temperature controlling devices in that engine, like later models like mine, you would want a pressure gauge if you used it at all. Would be a good idea since you don't have alarms like later engines to warn you of things.
