OMC fuel tank breather!

[deerhound]

I have only had boat about 2 weeks, never used it yet! but on buying noticed entire rear drenched in fuel, floor boards etc; I have stripped it all out and cleaned and dried everything, although the boards are now ruined with fuel/oil mixture,I now know the cause is the lack of a proprer breather on old OMC tank, (which is like new and I want to keep) I propose to drill a hole through cap on tank and epoxy in a piece of brass rod as used in model aircraft along with a length of silicone tube again used for model aircraft with say 2 model fuel filters for any dirt, I could either vent tank to outer skin of boat or keep pipe inside rear panel which I am reluctant to do, when not in use a blank piece of tubing over end of vent, can anyone see me causing further trouble with this idea? or does anyone think another cap with breather on would be better? I am surprised there was never an explosion due to amount of fumes and spilt fuel that was in there!!many thanks again for ant help. JBD.

 

[willamettejeff]

Re: OMC fuel tank breather!

Are you talking about an OMC 6 gallon metal gas tank? These are vented only when the fuel line is connected. Where is the fuel leaking from? If the gas fill cap and fuel connectors are in good condition, the tank should not be leaking. Also, were the tanks overfilled. The only time I've experienced any fuel leaking is from bad O ring seals in the connector ends of the fuel line. These can be replaced, but I just go ahead and buy a new fuel hose as the fuel line and primer bulb also deteriate with time and probably need replacing as well.<br /><br />Another cause for leaking could be from overfilling. As with any gas tank or container there needs to be an air space left for fuel expansion when temperature rises.<br /><br />These style tanks have been around for many many years and with proper use and maintenance should work safely and reliably. I think your trying to fix a symptom and not the cause of your problem.

 

[bayman]

Re: OMC fuel tank breather!

"I am surprised there was never an explosion due to amount of fumes and spilt fuel"<br /><br />I would be concerned about that too. If you do drill a hole in the tank, for example, that could be very dangerous right there since drills cause sparks. Even if the tank is emptied it will still have fumes. I have heard of welders filling tanks with water to make sure they don't have a problem. Of course then you would have to make sure all of the water is emptied after you are done.

 

[deerhound]

Re: OMC fuel tank breather!

many thanks gentlmen for help, the fuel tank that came with the boat and the one I refer to is a plastic 6 US Gallon tank with gauge, it has no vent on cap, seller showed me just to loosen it off a turn? I notice on bottom of tank year of manufacture 1971? it is perfect condition as is the Evinrude 40Hp and fuel lines, OMC control unit etc;,I would imagine that with boat pitching and rolling continually there is bound to be spillage with this set-up? can you think of any other way forward? other tank or new cap, do you reckon my breather idea is a Sledge Hammer to crack a Nut? I am most concerned about the fumes and spillage and would not run it like that, any help please would be great? JBD. "I COULDN'T FIX YOUR BRAKES SO I'VE MADE YOUR HORN LOUDER"!

 

[willamettejeff]

Re: OMC fuel tank breather!

What does the fuel line fitting on the tank look like? Does it have 2 posts the fuel line connector attaches to? Your tank may actually vent just like the metal ones do where the fuel hose attaches. Have you tried running with the cap on tight? Seems wrong to have to loosen the cap. May want to get a Tempo plastic or metal gas tank instead if this is the case. The plastic ones are not very expensive. In any event, you need to prevent the fuel from leaking for safety, health and environmental reasons.

 

[steelespike]

Re: OMC fuel tank breather!

I think what you expierenced was a leaky seal on the gas supply on the tank.It is suposed to seal when you unhook the gas line.I had one fail and it made the same mess.A vent wouldn't leak all that gas.A leaky supply would keep pumping out gas as the tank heated and cooled every time it heated it would push out a little more gas.On my tank the supply wasn't repairable.I replaced it with a good used one I had on hand.If I understand your discription of your home made vent it is way over kill and wouldn't work as described might even let gas out under just the right circumstances.My plastic tank had a vent knob in the middle of the cap(looks like a design feature)could be overlooked by an inexpierenced boater.Maybe yours has the same.

 

[deerhound]

Re: OMC fuel tank breather!

Thanks everyone for help, the tank when out of boat with some fuel still in (about Gallon) builds up fair amount of pressure just sitting as does anything with fuel in? it certainly has no vent and is totally original, the connector on the tank is the same as on the engine double affair, the fuel hose again is OMC origainal and I would say has double type connectors either end (FEMALE)top of connector has clip which locks it once it is on? two metal like valves one larger than the other, with a spindle protruding out which I say is a valve, now I am wondering if the system is supposed to run with tank closed? could this double connector be one for fuel supply and vent? although there is only one single fuel line?? Thanks again, any advise relating to this vent problem and tank set-up would really help and prevent me from disposing of a good tank. JBD.

 

[deerhound]

Re: OMC fuel tank breather!

I forgot to mention that the tank when it has fuel in it does not leak, neither does the fuel line or the connnection at the engine whether the engine is running or not, so probably if this double type connector is supposed to run with tank cap closed, the seller has been running it like that not knowing what he was doing, and passed the wrong method to me? what do you think?supposed to run with tank cap closed? JBD.

 

[deerhound]

Re: OMC fuel tank breather!

I have looked at the tank connections again, also have a Evinrude/ Johnstone manual (which is wrong year for my engine) my engine is 1984 this manual is from1991-1994 on page 361 Remote fuel tank it shows the type of connector mine is, On looking again at it it has two male ends on tank and on engine, one looks just to be support for when plugged in other end is fuel side needle valve/ spring loaded with row of holes around it trust this may help to end my fuel tank saga, somebody must have same tank?? JBD.

 

[willamettejeff]

Re: OMC fuel tank breather!

Also look on the tank connector for a couple 1/16 inch or so posts. These are actually valves that are depressed by the fuel line connector when it is attached and vent the tank. Like you when I originally bought my boat, I worried about the pressure that built up in the tanks with rising air temperatures and about the apparrent lack of a tank vent. I went so far as to replace the tank caps with ones from Tempo that included a vent. After discovering a few times after first having run the tanks dry that I had forgotten to open the cap vents, I realised that the tanks must already have a vent and I had wasted my money on the new caps. Let us know what you find.

 

[deerhound]

Re: OMC fuel tank breather!

Fine, I can't imagine OMC making such a nice tank without some means of venting it, surely even for the safety aspect nobody has to put up with fuel spillage? I just cant see that being the norm? and yet I looked at it for some time today,( cleaned it out with fresh fuel )still couldn't see a vent but I never tried connecting the fuel line which would I think have proved it?If one considers a full 6US gallons in it with the cap cracked open it's going to spill out, and even to minimise the amount would probably be even worse,I could send you a picture but I don't know how to put it on this site, I could provider my email address and then send you a picture to see if it is as you mention, but it is the ones in the Evinrude/Johnson manual.

 

[willamettejeff]

Re: OMC fuel tank breather!

Ok, send picture of tank and its connector to jtkane07 ..at.. comcast.net and I'll take a look.

 

[ndake]

Re: OMC fuel tank breather!

I had an old 75hp V4 Evanrude that had a tank with a vent screw in the cap. would not run without being open. I think the kind you have is vented through the fuel lines.

 

[imported_Curmudgeon]

Re: OMC fuel tank breather!

Your setup has been OEM for over 30 years, and has withstood the test of time. I'd run it with everything tight before making any drastic alterations. If it leaks, you'll know from where and can then proceed with confidence. If it doesn't leak, disconnect the fuel line at the tank when you're done for the day, make sure you don't overfill the tank, and loosen the cap for pressure relief (re-tighten before use). I'm betting your problem will disappear unless there's a seal/gasket leak of some description.<br /><br />BTW, plastic tanks are nortorious for leaking around the connector after a little use.