Hull Vents
 

I'm sure this has been asked a billion times but... What purpose do the vents on the hull serve? I've noticed some people remove them and some don't in the restoration photos.

Re: Hull Vents
 

They are a positive air flow for venting gas fumes out of the hull. If you look closely you will see that the vent fins on one side usually face forward and the fins on the other side face aft. As you run, air is sort of forced into and out of the inner hull. I believe that at some boat length they are Coast Guard required for ventilating possible gas fumes from the bilge. I could be wrong, but that is what I was brought up believing. I think the earlier 20's that had fuel tanks in the console did not require them. Newer models obviously all have them. Somebody else shoot me down on the law thing if I'm wrong.

Re: Hull Vents
 

If it's an I/O, Bilge/Hull vents are required as per Coast Guard regulations.Blowers that are ignition protected,and spark proof are also required,and should be run for a few minutes to exhaust any gas vapors.

The purpose,of vents and blowers,are to vent,and remove any gasoline vapors out of the bilge,that could send you on a nice amusement park ride,when you turn the ignition key.Gasoline vapors(if any) being heavier than air,settle in the lowest areas,and need to be removed
This is one of the regs.that makes sense,as boat explosions from gas vapors,are not all that uncommon.

They are not required(I think),on outboard powered vessels,but even they, can benefit from the vents.Any air, circulating through the hull and bilge is never a bad thing.

Re: Hull Vents
 

The requirement for bilge ventilation is for any vessel with permanently mounted below-deck fuel tanks. The requirement for bilge blowers is for any vessel with inboard engines.

Re: Hull Vents
 

So on our outboard hulls....just to add a little air flow? Should one side really be pointing forward? I have never seen that, but mine were not installed when I got the boat.

...and mine had a hose (like clothes dryer vent hose) going to the louvers from the bilge...is that necessary?

Also, I don't think people are filling them as stated above...just that some had them and some did not.

Another general question...seems like most newer boats and most other makes (even classics) did not have these...how are their bilges vented??

Re: Hull Vents
 

My 18's tank is in a sealed "coffin" box below deck. Why wouldn't that box be vented? There is electricity in that box i.e. sending unit wires.

Re: Hull Vents
 

Thanks for all the replies, I guess I'm more confused though than before as most boats with sealed coffins don't have them, I guess most are foamed these days so there is not much bilge to speak of!
I just bought a '79 23' CC OB and am most likely going to paint it over the winter, was just wondering if removeing them was an option, I will probably keep them just for the classic look anyway!

Re: Hull Vents
 

I bought my 1989 23 WA new and does not have any type of venting other than the hatches and it came with a 115 gallon below deck tank. I don't think they were required then otherwise they would have been a factory install. My boat came from the "Tampa" factory.

Re: Hull Vents
 

Boats are like women......its better to let them vent!!

Re: Hull Vents
 

Foaming in gas tanks is a BAD idea because the foam will hold water against the aluminum and cause it to corrode thru fairly quickly. This is why none of the original Moesly SeaCrafts ever had the tanks foamed in. Potter didn't foam them in either, at least up thru 72, but it sounds like maybe the later CSY and Tracker boats may have had foamed in tanks.

The early Moesly sterndrives had vent scoops but no bilge blowers, as I don't think USCG required blowers on inboards till about 1967. The idea of the vent scoops is to have them facing forward on one side to force some air in when underway and aft on the other side to suck it out.

Re: Hull Vents
 

Close. Forward facing in the bow and stern facing in the stern. Underway way, fresh into the bow and flushes the bilge to the stern. Even at anchor, the bow faces into the wind and in the forward vents and out the stern. The exception is smaller craft with only stern vents, then it is one faces in each direction.

Re: Hull Vents
 

To add tothe knowledge base - I know that 1978 and 1979s had foamed in tanks. Mine only lasted 28 years so that is not too short, but the failure did happen due to foam. The new tank is not foamed in.

Re: Hull Vents
 

Bushwacker, I recently changed out my fuel tank on my CSY 18' and was really pleased to find that the coffin box was not full of foam when I opened it up. I got 23 years out of the original.

Re: Hull Vents
 

SeaCraft is one of the few builders that provided a hatch so you could remove the tank to inspect it without tearing up the deck! That was the first thing I did when I bought my boat in 1975, and it was a good thing! During manufacture, someone had evidently dropped a brass nut used on the gages and the tank was resting on top of it! :eek: Needless to say, that creates a pretty good battery! Fortunately I caught it before galvanic action corroded thru the tank. Cleaned it up, painted tank with epoxy primer and original tank is still going strong! Pulled it again in 2006 when I repowered to replace all the hoses and it was still in great shape!

SeaCraft brochures also used to brag about not having foamed in tanks! They said it cost more, because then they had to ventilate the bilge, but they did it anyway because it made for longer lasting tanks!

Re: Hull Vents
 

My 1977 definately has a foamed in gas tank.....soon to be pulled out and replaced. Mine lasted 32 years!

Re: Hull Vents/Fuel Tank
 

Pulled my fuel tank yesterday. It was corroded all the way thru and leaking gas - YUCK. See attached picture. Just like everyone said, it was where the foam was in contact with the tank. Foam is coming out before the new tank is going in.

Jim
http://i233.photobucket.com/albums/e...enFueltank.jpg

Re: Hull Vents/Fuel Tank
 

The tank on my 1989 also had a leak, but was in the back and there was no foam in that area. Just powdered corrosion. It was a very slow seep until I had it out where I could see, put water in it and scrapped off the corrosion and the seep went from that to a pee hole. We did re foam the new tank,but put 1/2" poly strips under the tank to allow water to run out if any gets in. Then put mounting strips bottom front and rear instead of the side. My side mounting strips were loose, the screws had been worn out of the glassed stringers. The under deck platform was completely dry.