Maybe try just barely breaking the seal on the cover of the raw water pump impeller. If you have an air lock preventing the pump from priming, then the air will be relieved through the break in the cover seal. Don't go to crazy, or you will have to replace the gasket on the pump cover lid.
It would be possible to get an air lock, but if you have a globe impeller it should be able to pull water before burning out. You might have a bigger issue.
Dictated, but not read.