91 mercury 150, fuel pressure relief

[Captain Frank]

I have a '91 mercury 150 hp motor. I want to change the in-line fuel filter. In the service manual it says to always releive the pressure in the fuel system before unclamping any hoses or anything related to the fuel. They describe a little push-valve normally located on the bottom of the intake manifold, port-side. Well, I searched and searched, but can't seem to find this thing. Does anybody have any tips for me? Thanks.

[boats.net]

They are referring to EFI models with elect. fuel pumps. But it is always good to be carefull when working with fuel.