Mystery Thru-hull
 

What is the purpose of the large through hull on the bottom of the boat at the notch in the transom (dead center)? The thru-hull attaches via hose to a water dump thru-hull on the STB side rear. Does this introduce air into the props on take off?

This is on a 06 35 Lightning Twin Step.

my 38 has the same thing and im not sure what its for???????

It is for factory a/c

i have the same thing on my 38 still not sure what for .....thinking something to do with a/c .....but then again i have no a/c

Seems odd to poke a hole in the bottom of the boat unless you would be installing that option. Unless the mold has that opening integrated, but I doubt it.

It is a BIG through hull with a meaty hose running through to the BIG through hull on the side. Seems overkill for an A/C condesation dump.

29 Fevers' have had the same thru-hull, too, for a long time. I've never seen a 29 with a/c. I was told it was to break suction at the notch and assist in getting the boat up on plane (airate the prop?).

I have the same thing on my 35. according to the Lords at
Fountain it is for the optional a/c sys

Also it may be for a gen-set. I agree it is BIG

Since I have neither A/C or the GenSet should I close the gate valve (currently open) to that thru-hull? I wonder if while under way I get a cool blast of water coming out of the side thru-hull? Maybe that is worth leaving open! My Fountain's fountain.....

I have never seen one with a gate valve. All of the one's I've seen have been direct plumbed from the thru-hull in the notch directly to the thru-hull on the side. The only thing I've seen with a gate valve is the Fountain version of freshwater flush and that is usually installed on the transom. That has 1 quarter turn valve and 1 gate valve. Don't remember which way the gate valve is plumbed, but if you open/close that gate valve you will open/close water flow from the outdrive to the seawater pump and that would be bad for the engine! Regarding the vent to the notch, I've never seen any water come out the side vent - it pulls air to the notch, not pushes water from the notch to the side thru-hull. Hope this helps.

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.:party-smiley-020: