2017 DF 70 starving for fuel

[graynor]

Last year I repowered my 32 cat with a pair of 2017 DFI 70’s
Having major issues keeping them running. They bog down and then die. I pump the bulb and usually get them running again. Both engines are acting the same.
Heres what we’ve done this past year.
Replaced the fuel line with the best CG certified we could get.
Replaced fuel filters and installed electric fuel pumps to help prime the bulbs.
Replaced the bulbs and all fittings and clamps. The tanks are built in and about 20 feet and maybe 1 foot below the engines. We’ve bypassed the fuel filters thinking the the filters were restricting fuel suction to engine. We’ve drained both tanks and put new fuel in them. The dealer isn’t any help. His mechanic doesn’t have a clue! Once they get gas they run great. It’s a struggle to keep them running.
Any suggestions would be appreciated. I’m very mechanical inclined so no insulting recommendations like get a manual
oh BTW I’ve cussed it in Texan. Can’t speak it’s native language
thanks again

[boats.net]

If both engines are doing same thing then I would suspect the fuel tank if they are both running on same tank. May have bad fuel pickup tube in gas tank, bad anti siphon valves at fuel tank fitting. Might try running on a portable gas tank( get like a 6 gallon fuel tank and new fuel hose) connected at engine and if it runs good then move portable gas tank back to fuel/water filter then back to hose at boat gas tank to see which part of boat fuel system is at fault.