340 Overheat / Radiator Geyser

Update...Timing is now at 40 degrees total. I'm not sure what it was before I changed it (yeah I know), but the idle speed is lower now. No change. Meanwhile the gauge on my pressure tester that I went to storage yesterday to retrieve quit working, so there's that. Today I let it run only 15-20 minutes. This thing climbs to 1/2 on the gauge after only maybe 2 or 3 minutes. I have a thermostat and cap ordered. Temp gauge was just over half when I shut it down today. I did not get the dramatic immediate geyser, but coolant gushed out pretty good after only 2 or 3 seconds. Another big mess to clean on the roof. There is no spring in the lower hose. I have no air, water, or even electricity at my disposal here so I have to perform a 1-man bucket brigade from the 6th floor roof to my 1st floor apartment to be able to rinse stuff off. Thank God for Mr. Otis. As others have said, I-think something is plugged-up real good or the impeller is effed-up. The corrosion on the exterior of the water pump has me very curious. Remember I do the best I can with the resources available to me in an apartment in the city. Lots of pretty girls here in Nashville, though but none of them want me.