Problem maintaining gas hose pressure

[catsmeow]

Have a 95 90 hp Mariner. Having trouble maintaining pressure in my fuel line. Replaced hose and bulb and new female connector at engine. Run it in the driveway today at idle and bulb would go soft and engine stall out. Deceided to try removing the hose at the engine and the bulb is staying hard after like 4 hours. So thinking it must be a problem somewhere in the fuel system of the engine. Its a 3 cylinder, 3 carburator setup. Not good doing anything except changing lower unit oil and plugs. Any suggestions or do I need to just get a mechanic involved. Do not want to go out and have problems. Thanks..... Walt