Can not figure out my fuel problem. I have brand new Holley blue going to a Holley 850CFM on a BBC 454 build heads and mild cam. Boat runs amazing in drive way as well on the water idling. But as soon as I get on it or try to get on it all the fuel in front bowl sucks right out and boat falls on its face. Running 7 psi even tried upping to 10 but psi drops way low. No leaks in lines or in tanks.  Also getting 12.50 volts to pump when boats not running and 13 while running. Any help?

Yep, sounds like something is clogging the front needel/seat.

Thanks everyone. Sorry been so busy with work boat went on back burner. One of my fuel tanks was full of crystallized junk. Switch to mechanical pump as well and the filters where getting so clogged with fine stuff that is was causing lack of fuel. Couldn't get the tanks out and had to cut out my fuel tanks since apparently back then they fiberglassed them in. Now they are both clean and trying to figure out if I should glass them back or weld aluminum tabs on tanks.