Hull Vents

[bdenman]

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.

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.

[bigeasy1]

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.

[Fr. Frank]

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.

[ElBichoMalo]

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??

[76Red18]

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.

[bdenman]

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!

[gss036]

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.

[77SceptreOB]

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

[Bushwacker]

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.