Any through hull in a boat that is below water level should have a valve of some kind! If the connecting hose fails or leaks at the clamps it would wreck your day in a big way.

Thanks Gang!

bob t is correct. It is a vent to relieve adhesion, when the boat is breaking over on plane.

Bob T is right. Mystery solved

Was told by a long time Fountain employee when they started testing the 38- 42 Fountains with the notched transom, the first time they took it out to test it they started upping the throttles and the boat motors loaded up it wouldnt fall over on plane. Finally after giving it almost full throttle it fell over and it sounded like a 12 gauge shotgun went off. Thats when the decided they had to do something about the suction the notch transom creates on the bigger boats. The solution you already touched on.

Yes, this kind of nonsense has been around for 100 years, since the first stepped planing boats. Its pure BS. Air pressure is air pressure, air molecules are really small. If the air gets in there from a hose, exactly the same amount of air will ventilate the step from behind the step.

The sound of a shotgun? Come on. And the Easter Bunny leaves eggs on your lawn.

You really can't just see where the hose comes from? Try a flashlight and a mirror.

While the boat is on the trailer or lift take the hose and run
water into the through hulls located at the stern (not the gen set disscharge). On mine the larger through hull fitting on the starboard side is routed to the valve under the starbrd engine,and then through the bottom of the boat. You should see water exiting the
bottom of the boat. Obviously the ball valve / sea cock must be open.

Wait a minute...Who the helll is laying all those eggs on Easter then?

My buddies '96 '42 has the same thru hulls. Both are large in size and were just connected with a hose with no valve.
He used the lower thru hull for his A/C pickup.

I'll have to remember to ask him this weekend if he noticed a difference in his planing since the AC install this yr. Should be interesting.

I worked at the factory. Ventilation is it's purpose. Fountain is not the only manufacturer to use this on their boats.

Not sure if this is Chris or Thomas, must be Chris, dont think Thomas worked at Fountain, BK Millway, who used to work with the same dept. you worked with at Fountain, recounted the story to me along with some other neat stories. Could listen to him for hours. He is a walking encyclopedia when it comes to Fountains. How do those Easter eggs get their? Does Santa leave them.