the most likely cause is not enough fuel to the engine at high speed. Have you tried squeezing the primer bulb before trying to restart the engine? Does it feel soft or very hard?
The lift pumps on those model year Fichts were notorious for check valve sticking. After sitting a few minutes the check valve will unseat and it will pump again, for awhile.
I believe you need a new fuel lift pump or possibly a high pressure pump however the lift pump (low pressure side) is more likely the culprit.
Sincerely,
Evinrude-tech
Marine Mechanic
Evinrude Master Technician with 27 years of experience.