Not on this 32.

I don't even run mine. I figure with as much air flows through the vents, it should be good.

Might want to rethink your nonuse of them. They aren't for when you are running around on the water.
Air doesn't flow thru your bilge when your boat is sitting, or after you just filled up at the gas dock. That's when you use them.

I think the lines are to run your blowers at all speeds below plaining speeds???? I'd forget to turn mine back on after coming off plain, so I just leave them running all the time the motors are running.

Where did u buy those?

Do the blowers produce enough of a volume of air to open those flappers?

Yep. Work like a champ with zero problems. The internal flappers are an 1/8" poly material. Light weight, plus the pivot point is just high enough above center, very little flow is needed to open them do to the almost equal weight balance and pivot freely, yet the slightly higher amount of weight of the flapper below the pivot makes them close with no flow. Any water hitting them from the back just closes them even tighter.
All about ratio of surface area/weight, above/below the pivot pin and the fact they move with zero effort that makes them work just from the air flow.

Cool! I think I'll start running my blower this year.

Gasoline vapors sink and fill up the boat from the bottom up, both blowers should be sucking air from under your motors just above the bilge water - read lowest point in the bilge. The engine stringers divide the boat and make pockets on each side that need to be evacuated. They should be run before you start your motors every time. A loose battery cable or failing connection at the starter could create a spark and ignite any fumes. Gas could come from a loose fitting or hose or failing carb - whatever - it is not worth the risk not of not running them. I also have a fume detector in place under each motor too. If you have a diesel boat then the issue goes away.

So did u build them urself?

Sorry, forgot to answer, Yes i made them.