Tohatsu 18 loosing fuel prime ???

I have a Tohatsu M18E2 2-stroke. It runs wonderful, but when I shut it off, about 1/2 hour later, the fuel will have drained out (somewhere/somehow!?), so I always need to pump fuel with the hand pump, and sometimes it is a real pain to start the engine. It also runs rough sometimes after starting for a little while, like it's sucking air in the fuel line. This just started recently. Before that the engine started instantly with the slightest pull every time, and ran as smooth as silk.

I replaced the fuel tank (with a new quicksilver tank), fuel line and hand primer pump, and yesterday I even removed the fuel line connector at the motor and connected the fuel line directly to the fuel filter. It still looses fuel after not running for a while.

Thanks in advance for your help....

Is the new tank the EPA type, without a separate atmospheric vent?
Is there any visible fuel under the carb (dripped out)?
If not running, does the fuel system hold prime?

The vent is on the fill cap.
No sign of dripping fuel under the carb.
No - that is my problem. Withing 20 minutes of shutting it off it has lost prime.

Then the issue is gravity allowing fuel back past the primer bulb to the tank, Especially if the tank is low and the check valves in the bulb poor, that could happen. If you test by raising the tank up above the height of the carb and the problem goes away, you have diagnosed a leaky bulb.