PICS ADDED!!!??? OMC 6 gallon tanks, vented, non-vented, and fittings???

[Wishiniwuzfishin]

I have several factory O/E OMC 6 gallon tanks, some with the obvious vent in the cap and one that appears to have no vent. I have read before that even this tank should have a vent somewhere even if it is not obvious. But if the tank sits in the sun with the cap on tight, it builds up pressure inside because it "hisses" as the cap is opened. So if it does have a "hidden" vent it must be clogged.

But I believe I have also read that there are actually vent-less tanks and they are vented thru the fittings on the fuel hose. If this is true, IS THERE A DIFFERENCE in the fittings designed to be used on the normal vented tanks with the vent built in the cap and a non-vented tank?

Thanks in advance for any information.

 

[minuteman62-64]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

I have a new Attwood tank via Walmart. It has a one-way vent in the cap. It lets air in when fuel is being withdrawn, but has only limited ability to release pressure. You can't see it from the top. Turn over the cap and see if there is a little white "button" on the underside. That's what the one-way vent on my tank looks like.

Apparently the newer tanks have this feature to control atmospheric emissions.

 

[JimS123]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

The old OMC metal tanks were self-venting thru the cap. Kinda like a pressure relief valve. Sure you hear hissing or sucking, depending on the temp gradient, but if the pressure inside exceeds the specs, it will vent by itself. The best of both worlds - lets air in to run the motor and only vents gas fumes out if under high pressure.

 

[Chinewalker]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

The old OMC steel tanks with the male connector on top have a vent inside that connector. You will see a couple of tiny steel pins sticking out of the fitting. Those are spring loaded and will allow are into the tank as needed. They do not allow air out of the tank, which is why the tanks will build up a little pressure on a warm day. Keeps it a semi-closed system so you're not getting fumes in the bilge...

Those fittings are rebuildable if they leak. You'll see two aluminum discs. Those can be removed with a pick, allowing access to the vent pins and o-rings. One of these days I'll rebuild one and take pics of the process...

 

[Chris1956]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

A lot of the older OMC tanks had a two position cap. All the way tight would seal the tank for storage or travel. Open one click for motor use. Open two clicks to allow the tank to be filled. I never saw one that vented thru the fuel line.

 

[Rick.]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

A lot of the older OMC tanks had a two position cap. All the way tight would seal the tank for storage or travel. Open one click for motor use. Open two clicks to allow the tank to be filled. I never saw one that vented thru the fuel line.

Not thru the line. When the fuel fitting is pushed onto the tank the flat part of the fitting pushes a brass pin which allows the tank to vent. All my OMC tanks are that way except perhaps my 2 1/2 gallon tank. I'd have to take a closer look at that one. Rick.

 

[Wishiniwuzfishin]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

The tank I am talking about is a plastic 6 gallon OMC "SYSTEM MATCHED DURA-TANK" with a plastic cap. If there is a vent on it somewhere, it is "invisible to the naked eye".

TO CHINEWALKER AND RICK: Are there 2 types of OMC fuel line fittings? One
that vents thru the fitting and one that doesn't?

I'm wondering if I can use the same hose and fittings on this tank that I use with the tanks with the normal screw type vent in the cap.

 

[F_R]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Only one kind of hose fitting. The outlet valve assembly on the tank contains the push pins and vent. The hose fitting pushes the pins in.

Not sure of the Dura Tank. I'll have to look into that. Help me do that by telling us what year the tank was made.

EDIT: Is this your tank? If so, sorry but I don't know much about it. Too new for me, I'm and old motor guy---like "1957 Evinrude" is.

But it is safe to say that emissions laws prevent discharge of fuel vapors, so tanks are vented one way to let air in but not fumes out. Heck, now they have even outlawed the sub-microscopic molecules that escape through the rubber hose!!! Beginning next year, people won't be allowed to pass gas either.

http://www.marineengine.com/parts/j...0JEOD&manufacturer=Evinrude&section=Fuel+Tank

 

[Wishiniwuzfishin]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

I've looked for something on the tank to date it and I can't find anything. I have 12 motors and 3 boats right now and I can't come close to remembering which motor or boat I got it with, if I even did get it with one of them.

Sorry. I'll go look at the tank again.

 

[Wishiniwuzfishin]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

OK With a little closer examination, and the help of a magnifying glass, I found this information:

Commonwealth of Massachusetts
Approved Portable Gasoline Container
Date 5/7/90 (guessing at the 9 but I don't know what else it could be
Approval number PC-150

Also found what looks like a code for the manufacturing date that looks like little clocks with the date:

3 Month
2 Day
0 Year

So I am guessing that since it had to be manufactured after the approval date it must have been made in 2000 or 2010 and I'd guess 2000 but who knows.

But it definetely has "DURA-TANK" in big letters on it so this must have been it's marketing name.

 

[Wishiniwuzfishin]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

That tank in the link you posted FR looks exactly like mine.

 

[Rick.]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Well I have to say I was only speaking from very limited knowledge. I thought we were talking OMC METAL tanks. Sorry if I lead anyone down the wrong path. I am embarrassed to say I didn't know OMC made a plastic tank but it makes sense that they moved over to plastic. Rick.

 

[Wishiniwuzfishin]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

My fault too. I tried to include what I thought was enough information in my original post, but left out a big piece of information. It is a plastic tank.

 

[JimS123]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

A lot of the older OMC tanks had a two position cap. All the way tight would seal the tank for storage or travel. Open one click for motor use. Open two clicks to allow the tank to be filled. I never saw one that vented thru the fuel line.

Whoa! Better not run the motor with one click open or you'll slosh fuel around when you hit a wave. The first click is to releive the pressure when you want to take the cap off. Otherwise, the cap may fly off and hit somebody in the face. Its run all the way tight all the time except when filling.

 

[JimS123]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

The old OMC steel tanks with the male connector on top have a vent inside that connector. You will see a couple of tiny steel pins sticking out of the fitting. Those are spring loaded and will allow are into the tank as needed. They do not allow air out of the tank, which is why the tanks will build up a little pressure on a warm day. Keeps it a semi-closed system so you're not getting fumes in the bilge...

Those fittings are rebuildable if they leak. You'll see two aluminum discs. Those can be removed with a pick, allowing access to the vent pins and o-rings. One of these days I'll rebuild one and take pics of the process...

The pins activate a valve that seals the line shut. Otherwise, if you took the line off and tipped the tank it would leak out.

The fuel line does not "vent" the tank when running. If it did you would have fuel going one way and air bubbles the other way. Not efficient mass transfer.

The old 2-line pressure tanks vented thru the fitting and the entire tank was sealed.

 

[Chinewalker]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

The ads I've seen for those Duratanks mention a "vented fuel cap"....

 

[Haffiman]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

The Dura tanks were delivered in a couple of versions.
Some were 'sealed' and used a vent screw in the cap. Some had a yellow plastic tab sticking out and was pushed in when the connector was put on. That tab both opened a vent and fuel. On some of the first versions a service bulletin was issued concerning a Blue O-ring inside that failed.
Bottom line is:
If you have a Dura Tank WITHOUT the yellow tab at the connector, use a vented cap.
If You have the yellow tab, use any cap, vented or not.
Biggest problem with the Dura Tanks was that they ended up as balloons if left in the sun and fuel hose not connected or cap vent closed!
Added link:
http://www.powerboatcentre.co.nz/vmchk/fuel-tanks/dura-tank

 

[Wishiniwuzfishin]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Pics added. Would have done this earlier but was having trouble getting pics from camera to computer.

Pic of inside of cap looks like it might be a vent, but I can't see any hole or anyplace where it would actually vent thru.

No plastic yellow tab either.

 

[Haffiman]

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

Re: ??? OMC 6 gallon tanks, vented, non-vented, and fittings???

On pic 2, under the locking pin for the connector a square hole. Behind a membrane - the vent hole.