I haven't counted out a perry system, and your point about the vent taking in water I considered also. The carbs do need pressure per instructions, I was just trying to get away with a more simple closed system which by others the webra's only been needing pipe pressure and a good tank location.

The vent I guess could be delt with just simply pointing it upside down in the boat, or a snorkel where when its capsized would clear the waterline.

So with the vent problem solved Im going back to the ideas again.