I had a 9.8hp of the same vintage that would do the same thing. One of the check valves in the fuel pump was stuck, so it would not pump well, and these pumps are small to start with. Ran great with the tank up high. Unsticking the check valve fixed my issue.
Member Pine Tree Boating Club chapter of AOMCI
"I don't fully understand everything I know."
"There is nothing — absolutely nothing — half so much worth doing as simply messing about in boats." (Kenneth Grahame)