# old style metal gas tanks. Worth the trouble?



## santeerangerman (Oct 22, 2014)

Was helping a buddy clean out his granddad's old shed, and came across a metal, OMC 6 gal tank. Except for some surface rust on the outside, the tank looks to be in pretty darn good shape. Bottom of the tank on the outside looks near perfect. Zero rust and the paint still looks good. Inside of the tank looks pretty clean, with a LITTLE old gas/oil residue along the edges. I know the gasket around the sight window will need to be replaced.

So, is there any way of checking the tank for leaks? I was thinking about pumping about 6-8psi air in it and spraying the seams on the outside seam with some soapy water.


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## earl60446 (Oct 22, 2014)

If it does not leak and there is no inside rust. Just clean out the inside and use it. Nice thing about metal tanks is they don't blow up when the sun is beating on them.
Tim


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## santeerangerman (Oct 22, 2014)

earl60446 said:


> If it does not leak and there is no inside rust. Just clean out the inside and use it.* Nice thing about metal tanks is they don't blow up when the sun is beating on them*.
> Tim


 Precisely! Summers here in SC ain't exactly cool either. I've seen the plastic ones swell up so much, you'd swear it was gonna rupture any second...


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## Johnny (Nov 1, 2014)

When cleaning any old metal gas tank, I put a few hand fulls of coarse 3/4" gravel
and some water in the tank and shake the heck out of it to break any loose scale or rust from
the inside surface. Not just a couple of baby shakes, I mean shake the fool out of it.
Remove rocks, rinse well, place it in full sun to dry out. Wire brush any outside rusty
areas to make sure the metal is solid.
At night, put a strong light into the tank and check for any pin holes.
Also, if you can pressurize the the tank with water, that is also a good idea.
Anything to detect pinhole leaks. Then, you will feel better about using it in your boat
without the fear of having gas leaks leading to a potential fire hazard.
If you do have some small holes, scuff the area with rough sandpaper and dimple the area with a hammer,
Then, fill the dimple with Fuel Tank Epoxy putty. Sand smooth and paint it.
https://permatex.com/component/virtuemart/adhesives-sealants/permatex-fuel-tank-repair-detail?Itemid=0


and like the others have said, the sun can really put some pressure on a fuel tank !!!!

Jus my dos centavos


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## earl60446 (Nov 1, 2014)

Barefoot_Johnny said:


> When cleaning any old metal gas tank, I put a few hand fulls of coarse 3/4" gravel
> and some water in the tank and shake the heck out of it to break any loose scale or rust from
> the inside surface. Not just a couple of baby shakes, I mean shake the fool out of it.
> Remove rocks, rinse well, place it in full sun to dry out. Wire brush any outside rusty
> ...



Why water? Seems like something that won't cause rust would be better.


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## turbotodd (Nov 1, 2014)

So no one has mentioned the downside of metal tanks.

They are vented. They had to be, but not vented like today's high quality plastic tanks. I'll get to the vent in a minute.

metal does an excellent job of allowing condensation to form inside the tank. This is especially true if the tank is allowed to sit out in the elements and where temps can change drastically. Like here today, this morning it was 30°, this afternoon's high was 69°. Almost a 40 degree change. As the tank get hot, then cools off, water vapor in the air condenses. 

With the vent working both ways (allows air in and air out), condensation occurs faster and more severe. Also, today's fuel pretty much sucks. 40 years ago when metal was the only option, gasoline would not evaporate like it does today. Take a fully vented full tank of fuel and let it sit outside for a few days. I bet you money that some of it will be gone. During the evaporation process, the fuel cools off, which also invites condensation to form in the fuel. You can see this quite well by using a quart mason jar about 3/4 full of fuel, lid removed, and let it sit out for a day or so. Even in a few hours you will see the effects, I tested it a bunch of times at work and on hot humid days, you could watch condensation form on the outside and inside of the jar. In about 2 hours, about 30% of the fuel had evaporated and there was an ounce or two of water (condensation) in the bottom of the jar.

This is why the "new style" fuel tanks were invented. Well that's one reason, the other was EPA regulations requiring low permeation materials so that fuel would not permeate through the material and into the atmosphere. Down side is that low-perm material is more expensive. BUT the venting system is a little different in that it will allow air to come into the tank as the fuel is used but won't let pressurized air escape. This is why the tank swells. The cheapie (attwood, etc) tanks will swell up a LOT because the material is thin. I do know that an OEM Yamaha tank is a good bit thicker material and therefore doesn't swell nearly as much. Also, since the low-perm tanks don't vent internal pressure to the atmosphere, they won't allow evaporation, and don't allow condensation to form inside. I do not know of the other OEM tanks ('zuki, BRP, Merc, etc) so I cannot compare them. When I sold Merc (brunswick) they were all metal and a plastic tank was not even available yet. When we dumped Merc and went to Yamaha exclusively, we started seeing plastic tanks and thought that it was a move in the wrong direction. But there were no issues with them. We went to Yamaha for many reasons and the statement was made by a fellow tech that we would be working on more outboards. Nothing has been further from the truth. By Y2K they were mostly plastic. In 4/2011 the low-perm tanks started showing up. I thought they were going to be junk. But I was wrong. They are heavy and of a material that is pretty tough. Also, the new EPA compliant fuel lines are of better quality than the wal-mart lines are-they don't harden up. You pay more, but you get better quality. A new 6 gal tank and line is around $120. But figure in what an Attwood costs and an Attwood line costs, and multiply that by 2 or 3 times that it has to be replaced. They've gotten better, but still nowhere near the quality of the stuff that I have to deal with from Yamaha.


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## Pappy (Nov 2, 2014)

The old OMC metal tanks that had the non-vented metal screw on cap were and are excellent choices. 
How do these vent? 
They vent by compressing a small plunger when the fuel fitting is attached to the tank. 
The plunger opens a tiny valve that only allows air back into the tank as fuel is expended or used. 
Disconnect your fuel line and the tank is not vented. 
The ones with the vented screw on cap are also excellent as long as you remember to close the vent. 

Keep the tank covered with something and the possibilities of internal condensation is also lessened. 
In my Gheenoe I keep my throwable cushion on top of my metal 3-gallon tank. Keeps the tank cooler and the sun off of it. Less issues all
the way around. Was in the boat for over three years now and no water ever. Was stolen out of the boat a month ago so now I hope it fills with water and strands the low life at the farthest point from shore.......


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## shawnfish (Nov 4, 2014)

ive never used nothing but the 2 metal omc tanks that were bought with my motor in 1980 and have never had any issues. all that's has been done to them is emptied every winter and pour some oil in them and shake it up real good then rinse out with a little gas in the spring and fill it back up with the fuel/oil mix.


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## lswoody (Nov 8, 2014)

Barefoot_Johnny said:


> When cleaning any old metal gas tank, I put a few hand fulls of coarse 3/4" gravel
> and some water in the tank and shake the heck out of it to break any loose scale or rust from
> the inside surface. Not just a couple of baby shakes, I mean shake the fool out of it.
> Remove rocks, rinse well, place it in full sun to dry out. Wire brush any outside rusty
> ...



I agree. Even a little bit of rust inside can be a pain


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## Daretofish (Nov 17, 2014)

They didn't last as long around here in the salt water, they are non-permeable though! I think I've come to like the plastic for how easy they are on the boat. Some friends use them for display purposes or on the motor stand.


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