I'm working on a similar situation, so here are some thoughts. Check all the fuel hoses, and vents. Check the fuel hoses from the fuel filler hose to the tank, from the tank to the filters, the return hose from the engine to the tank. There is also a vent hose that goes out the transom - sometimes spiders like to plug up this outlet. If you can't find it by feel, try blowing powder around on the inside bottom of the boat. Then check in a day or so for traces of fuel that have run down the powder.
[Non-text portions of this message have been removed]
