It really depends on a number of things, like whether you are fuel injected or carbureted, length of wire, etc.. In my IO setup, with the legacy Airflow Performance high-pressure pump and filter (P/N 3090050), the instructions say this:
"This pump package will draw 5 amps at 12 VDC. The pump should be protected by a 10 amp. circuit breaker. Electrical wiring to the pump should be a minimum of 16 gauge stranded wire. The pump is supplied with 14-gauge wire."