I/O ventilation

[oldfielder]

Anyone have a picture of where and how the blower is mounted in the bilge of your I/O. I've been thinking of the volatility of gas fumes a little lately and would like to avoid any big bang-I read on a coast guard reg related site that the vapor from one cup of gasoline in an enclosed space can have the explosive power of five sticks of dynamite
I have a blower, but in my research it seems that it is supposed to be tied to one of the ducts via/ a flange. Mine is mounted high on the inside of the transom and simply serves to move air in the bilge, but is not directly fixed to any of the flex tubing.
I understand that the seacraft has a natural venting system, but I'm not sure how to rig this coast guard required blower.
Another thing: do most of you have the louvers on the front vents facing fore or aft? I'veseen many facing aft, but that seems to defeat their purpose of introducing air into the vent system.
Thanks
Doug