Engine cuts off on high speeds after about 5 min

"On my 1999 Mercury Optimax, i

"On my 1999 Mercury Optimax, it runs great if i don't run 3/4 throttle, but after 5 min. of running at 3/4 throttle, it cuts off like it's not getting gas. Batteries are fine b/c it'll turn over and fire for like 5 sec. but it will not run for more than 10 sec after it finally starts up. Any ideas what it could be? We replaced the bulb on the fuel line, the fuel filter and the thermostats already, but i was thinking it might be the fuel line...it's a 3/8" diameter line now but maybe i should get a bigger line? i don't know? Anybody know what might be wrong or what i can try? thanks again.

-Preston J"

"its not the fuel line. is it

"its not the fuel line. is it getting hot, does the warning horn work? if you want to rule out the fuel line just pump the bulb when it starts acting up"

"Sounds to me like it's ge

"Sounds to me like it's getting hot, have you ever replaced the impeller? If not that's where I would start"

check fuel and air pressure

check fuel and air pressure