[Gerry Zagorski]

Sounds like you looked at all the places I would have. Are you sure you changed all the fuel lines? Reason I ask is I had a friend who had the same issue. After spending lots of time and money replacing things, it turned out to be very small section of fuel line hose they didnt replace that was collapsing on them.

Sounds like both motors are having the same issue, right? If so it would seem to me that it has to be something between the tank and where the fuel line splits to feed both motors. This is where would start looking around. You could try to run the engines on portable tank at different locations of your fuel system to try and narrow down your search. Maybe start by disconnecting the fuel line from your tank, run that line directly to your portable tank, run the boat and if it checks out OK then you know it's something having to do with the tank, vent, check valve etc. If it does the same thing then it has to be something upline of the tank and you'd work you way upline bypassing other components that are inline heading towards the engines.

Best of luck Fly.... Let us know what you find.