1973 Mercury 500 50hp fuel pump issue

[Heavyduty 2000]

Working on a buddies boat. The motor runs good but the fuel pumps are not pulling fuel into the carbs. It runs great but you must manually pump fuel to the carbs. Pulled carbs and replaced all gaskets and diaphragms still will not pump. Replaced all fuel lines to rule out an air leak still nothing. When the engine is running and chokes down because of not enough fuel the filter bowl is still full. I am out of ideas. Please help I want to go fishing. lol The diaphragms and fuel lines all looked good.

 

[The Force power]

Working on a buddies boat. The motor runs good but the fuel pumps are not pulling fuel into the carbs. It runs great but you must manually pump fuel to the carbs. Pulled carbs and replaced all gaskets and diaphragms still will not pump. Replaced all fuel lines to rule out an air leak still nothing. When the engine is running and chokes down because of not enough fuel the filter bowl is still full. I am out of ideas. Please help I want to go fishing. lol The diaphragms and fuel lines all looked good.

Have you tried to; give it fuel from a jug/other fuel-tank? (to eliminate blocked pick-up tube)