Trying to track down a recent (didn't change anything) overheating problem on my 73 d200 with a 360.

When I start the engine from cold, it gets up to about 230 after roughly 6 minutes of idling or low rpm in park before I turned it off. The upper radiator hose never warmed up in that period of time. I took the thermostat out to test (and it was in plenty of water in the thermostat housing), and it's opening at 180 when I test it in a pan of water. The radiator is full, and I don't see any leaks. The thermostat, upper and lower radiator hoses are all fairly new (1-2 years), and it had always been running at normal (180ish) temperatures before the past couple of times I've driven it.

Does that indicate the water pump itself is bad? It seems like it's not pumping otherwise I think the upper hose would get hot at 180+ degrees (certainly by 220+), yet when I think of a "bad water pump" I usually think of leaking which I don't think it is.