70 Johnson problem

[Blue_Runner]

An obstruction can cause your primer bulb to collapse (suck in).

I don't know if that's your problem, I'm thinking not, but probably would be simple enough to run it on a separate fuel line and portable tank to eliminate the possiblity of an obstruction.

Other than that, and the fuel pump, I would have to consult the experts on this site. Skools could probably help as he is a "Johnson" man. ;)