model#J175GLEDB

A couple months ago I had a question regarding the fuel pump. I can idle it in my yard with the water boot hooked up you can throttle down and it seems like it wants to run. When it is in the water and you go to throttle down it acts like it runs out of gas. You can pump the bulb while going and it will run fine like there is nothing wrong but as soon as you stop pumping it'll die. I had the fuel lines check, didn't see any cracks. Changed the vro fuel pump and it still is doing the same thing. I was told by the mechanic (who I am loosing faith in) that there is another fuel pump. Just wondering if they were referring to the pump assembly vapor according to the schematic breakdown of the fuel bracket and components.

Any other ideas as to what it may be?