Now them is great engines! What you have is an engine that likes to run hot. They are the darnedest hot runnin things you'd ever hope to see.
Make sure you have a NEW 195 deg thermostat in there. Then look to the radiator cap. Put a new one of those in there too. Those are the cheapest fixes you can get for the old girl. AND either one of them can be the problem.
Now for the gauge.. Motor homes gauges do not always display correctly.. Keep that in mind.
You did say it was blowin steam. If so then do the thermostat and the cap first and you might have the problem fixed.
Remember a colder thermostat can cause the engine to heat up!
Big JIm