I don't think it's vapor lock. After 2 days of sitting and me cracking the water separator (full of fuel btw) it still wouldn't fire off... I would think if it was vapor lock, it would have worked its way out after 2 days...

Check for fuel pressure at the rail (42psi) as said before and if there is none check for power and ground at connector on pump. If power and ground are good and no pressure its the pump. If you have no power at pump check the fuse in the wiring by the ECM. I had a fuse crack, yes crack not blow, I checked it on the water and it "looked" ok but under closer inspection (putting on the cheater glasses) I found a crack in the fuse. Put a new fuse in and all was fine. Good luck

There is no return from the fuel rail on those engines so it very well could be vapor lock.
Cycle the key a few times before you attempt to fire the engines. This will load the fuel rail, fuel filter and hoses with 40+psi of fuel. If it does not fire then, check for spark.
The easiest way is to check fuel pressure at the rail like I said before. You can rent a fuel pressure test kit from Auto Zone, O'reiley's, etc.

Not always. Mine wouldn't even try to start for quite some time. After several key cycles and long cool off period, it would sputter and stall until the "bubble" was passed.

It should start after setting 2 days. When I had vapor lock, I would get towed in (10-15 mins) to find the damn thing start when I got it on the trailer.

So the pump does run for a few seconds with key on, engine off? Do you have spark? (spark testers are cheap - and you should use one, don't use a screwdriver). I'd also suggest a fuel pressure gauge.

Finally had a chance to work on the boat. Found the fuel pump to be bad. Swapped the port over to the stbd (bad side) and she fired right up.

Good deal!