Through hull water pickups

[bwells]

I've noticed that as well on my prop wash pickups but I chalked it up to slower speeds lets the siphon idea take effect and you once more need to fill the tubing as speed increases. Check valves would not help ( I don't think) as it would be a restriction in the flow. I just need to learn how to run balls out all the time!

[785boats]

I used a couple in my old Thornycroft Torpedo boat.
They are located just in front of the step either side of the keel.
Yes in 1914 they had stepped hull Torpedo boats.
This boat would be lucky to reach 20mph & there is plenty of water flow from them. So I'm sure they would work on your airboat at the transom
Here's a pic of the underside of the hull during construction, showing the step & one of it on the run.
I don't have a pic of them installed but I could take one if you want.
Cheers.
Paul.