Gary,
There is nothing behind the valve except the white plastic screen.
You will need a VERY thin wrench to disconnect the shut off valve from the
fuel pipe.
We used to call that type of wrench a tappet wrench. I could only get it (as
it is metric) from McMaster Carr. I believe that our filters stay so clean
as the fuel is drawn off the bottom of the tank. Thus, you never get a
biology experiment growing in your yank- unlike US boats that have a pickup
tube and allow stuff to build up in the tank.

With careful use of a soft copper pipe as your pickup tube on the "tank
vacuum" you can get to almost all of the tank from the forward inspection
port as there are holes very low in the baffles that allow the pipe to snake
into the other chambers.

I have attached a pix of the Racor system used to pre filter the fuel.
Mine is identical to this one from Ian & Judy Jenkins amel Pen Azen.


Fair Winds,
Eric
Amel Super Maramu #376 Kimberlite