No wonder the guys with boilers need power....can't heat with gravity.
When my parents' sole source of heat was a wood boiler in the basement, we'd manually open the solenoid valves and have plenty of heat. Just had to keep a close eye on boiler temp because the automated controls were down and we had to control the air intake manually. Overheating wasn't generally a problem because we'd cook ourselves out of the house long before the boiler hit 200.
The generator ran the freezer and refrigerator. When it was time to water the cattle, we'd wire a plug to the well pump controller and plug it into the 240 outlet on the generator.