Thanks for the help but Where is this check valve at.My 2002 5.0 MPI would do this. I discovered it was the check valve assembly (part #21-864206A). The internal valve had come apart and I believe it was allowing hot water from the block to back fead into the fuel cooler. This would happen on occasion after sitting for 30 -40 minutes the boat would turn over but fail to start as though it was starving for fuel. Before I discovered the bad check valve I would loosen the fuel filter looking for a solution and this would seem to help a bit. Replacing the above part is what fixed it. Not sure this applies to yours. My 2 cents.
We may never know what fuel system the op has...Mine is #2 in the attached. Port side low and back. Yours may be entirely different.View attachment 337221
What the guys are looking for is an engine serial number or is the engine carb, efi, or mpi the answer you get will depend on what fuel system you haveThis is a 5.0 305 CID. Thanks for the replys. I'll check everything