Rust in bottom of 6gal gas tank

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paradactal

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Not sure if this is the right forum but I have these 2 gas tanks that I got with a boat I picked up. One is 6g and the other is a 3g. Both have a little bit of rust in the bottom of the tanks. Is there a way to get rid of the rust an use them again. I hate to scrap them and buy new ones. The rust is in small patches on the floor of the cans.
 
im not sure if its a good idea but i put some small washers in mine with some fuel and shook away for awhile to get anything loose out of the tank
 
Personally for how cheap gas tanks are i wouldnt waste my time trying to get it clean.

Its not worth having one piece get hung up in yer carb...

IMHO
 
Throw a hand full of 1/4" or 5/16" nuts in the tank and shake them around.
 
Also check into electrolysis tank cleaning. There is tons of info on the net.
I did this to clean an old '54 motor tank and it worked great.

If there is a worry about crud left in the tank then a filter can/should be put in line with the tank (should have one anyway).
 
Concrete cleaner. which is Muriatic acid (or hydrochloric, IIRC).

Stuff is STOUT. I have done many many motorcycle tanks over the years, and a handfull of automotive tanks as well. Those are fun (not).

Drain the entire tank. You'll need your muriatic acid. And a "Kreem" kit from a motorcycle shop.

Remove any sending units it might have. Fuel gauge? Take it out.

First rinse the fuel tank with water. Lots of it. Warm works better than cold (hot is nice too). Rinse it out real good.

Then grab a hand full of rocks from the driveway. I have a long gravel driveway so I have plenty of rocks and just perfect for stuff like this. Drop a bunch of rocks inside the tank with a little water. The water helps slosh the rocks around and keeps the rust flakes from getting under other rust flakes. The rocks bust the big stuff loose-if there is any. If it's just mild surface rust (and you can't see any flakes), the rocks aren't really needed.

Next step. Get some goggles and breathing protection, as well as some protection for your hands & arms. Muriatic can kill you if you try to drink it (hint). If you inhale the fumes, they will make your nostrils and airways all the way to your lungs feel like fire for a couple hours (experience speaking). You get it in your eyes, you'll be using a dog to drag you around. It's bad stuff---but for what we're doing here, it's the only thing that works. I usually use about 20%-25% (about 1/4) acid and 3/4 water. Soon as the stuff hits the rust, you'll know it. You will see steam and other bad stuff coming out of the tank. Slosh it around, all around inside the tank. bottom, top, sides, etc. Dump it into a plastic container and then treat it one more time. Normally 2 treatments are all that's required. If it's REALLY nasty, buy a new tank. The acid works pretty fast so you have to watch out...it "can" eat through the tank if you let it sit in there for a while at full strength.

Then you'll want to rinse it out REAL good about 2 or 3 times to get all the acid out. The last rinse, I like to use warm or hot water as it dries faster.

In the Kreem kit, there is some acid. Dispose of it. It's garbage. It works to brighten aluminum (or turn it black) but that's about it. The #2 bottle is a strong alcohol that helps to remove any water from the crevices. I use it, and all of it on a steel tank. Then dump it out. It also has some nasty fumes but not as nasty as the acid. Dispose of it carefully as well. It will evaporate quickly and the tank will get cold as it evaporates, and I usually suggest setting the tank in the sun while the stuff evaporates out. If not, it can draw moisture via condensation-and Kreem will NOT stick to moisture (which is why they send the alcohol, to help remove the moisture).

The last step is the actual tank liner. The "kreem" as I call it. It also has fumes; about like the alcohol. You will dump about half of it into the tank and slosh it around where it will coat the entire bottom of the tank. Once it's evenly distributed, dump the rest in and coat the rest of the tank, sides, top, everything. It takes a while and a lot of "sloshing"....but I tell ya, the stuff flat works. Done properly, the tank will never rust again. It is a plastic liner.

The kit itself is about $45 last I checked. The muratic is cheap. A gallon is like $3. You can buy 20% or you can buy the good stuff...the choice is yours. I get the good stuff because I dilute it anyway, and a gallon will last many tanks. BTW, dont get the acid anywhere near anything else metal that you don't want rusty. It cleans concrete REAL good too...and will streak it a little sometimes. The time it takes, well, on a typical 6 gal steel tank with a fuel gauge, it takes me about 4 hours from start to finish if I'm not hurrying...and you don't want to hurry. The liner needs to set up over a period of about 48 hours (the bottle says 24 hours...but IMO, minimum 48 hr). I usually like to do it in the morning so I can move the tank around & evenly coat the entire inside of the tank before the stuff sets up; then let it sit overnight and all the next day. Then it's done.

Given the chance, I'd buy a new tank...especially considering today's fuel quality. Fuel evaporates quickly nowdays. New tanks are designed to stop (or slow down) the evaporation process by not using a vent, or at least using a one-way vent. The old style tanks with vented caps WILL allow moisture to form inside the tank if it sits for more than a few days. Fuel evaporates, the tank and fuel temp drops (evaporative cooling), and moisture from the air condenses. New tanks without a vent won't let evaporation take place as fast. And with the price of a Kreem kit plus all the rest of the goodies to go with it, you're right back to the price of a new tank. I like the new EPA compliant Yamaha tanks. Lot thicker material and they don't swell much; unlike the Attwood I used to have that broke due to swelling....while I was fishing on the lake). Not fun.
 
+1

Unless you're trying to save a rare antique tank or your grandfathers old tank which has sentimental value, it's not really cost effective to restore one. As mentioned already, by the time you figure in the cost of the liner kit like POR 15 or Kreem, add all the labor to clean and install the liner, you will be really hard pressed to justify it. If you're still determined to restore one though, the POR 15 kits come with all the chemicals you need to clean the rust out, prep the interior, and line the tank. If you just want to remove the rust and forget the liner, I'd recommend using Oxalic Acid. It's milder than muriatic acid, which has the potential to eat a hole in your tank if you don't know what you're doing, and the Oxalic will leave a protective coating on the metal which helps prevent future rusting. I've watched several vids of the electrolysis method and it appears to work very well but I've never tried it myself.
 
If it is a couple of small patches of rust I would certainly not scrap the tanks. You can use the nuts and bolts method pretty easy on the small patches of rust with great results. If you don't feel like shaking a tank around then you can do the electrolysis method and that works with about zero effort !
 
Wow! Some really great info. The patches are about 2"x2" or so. It's definitely not a family heirloom. Just didn't have the $100 for a good tank right now although I did find a metal 6 gal on Craig's list and am picking it up today for $40 with hose and bulb. So hopefully that looks good on the inside. Thanks again for the terrific feedback and ideas. I love this site already!
 
What do think about using Phosphoric acid inside the tank and maybe add some rocks and shaken a little bit? It kills the rust and changes it to a primer coating.
 
Phosphoric is what the Kreem kit comes with. Pretty weak, IMO. Might work for surface type rust though. I never use it for time constraints. Cheaper to pick up the $3 gallon of muriatic and spend 30 seconds with it as opposed to the phosphoric that comes with the kit, that takes up to an hour to remove big stuff. Muriatic does exactly the same thing, just a LOT faster. Etches the metal so the stuff with stick to it.

I've also used red-kote and had mixed results with it. Some worked well. Others peeled loose. It is cheaper than Kreem but doesn't come with the metal prep (acid) and the alcohol like Kreem does. Never used POR-15. Kreem and Red-Kote is all I've used.

Red-Kote doesn't agree with diesel. Doesn't apply to outboards but it is an FYI.

Kreem also doesn't like acetone. Brother tried to run his old 4 wheeler on Acetone and the Kreem liner ended up in the carb. Nasty mix of stuff.
 
OK, now I'm a little overwhelmed! I just bought a used 6gal tank and it looks pretty good on the inside, BUT, I dont have the right connections. I have 3 tanks now all with different fittings. I am trying to hook up a 1975 Merc 20hp. Forgive me for my ignorance but it has the round connection to the motor. The tank I just picked up has a different connection to the tank. The tank I want to use has a 2 barb connection at the tank. I need a 2 prong connection at the tank and the old style round mercury fitting to my motor. Can someone link me to a complete setup like that? Also, to call a hose assembly in good condition, how should the fuel line be? My fuel line is rock solid and I cant take it apart to build anything. Its not pliable at all. Should it be? Everywhere I look, a new tank and fuel line looks like its going to run around $150 for the whole setup. Add $25 to that at my local boating shop if I get something tomorrow instead of ordering on line. Just seems like its pretty overpriced for a dang fuel tank and line? A little guidance here would be greatly appreciated
 
You're going to have to build your fuel line or modify an existing one. If the line you have now is hard, you need to trash that one. If the bulb is hard or has dry rot cracks in it, it's trash too. You can buy a bulb, line, and connectors separately.
https://www.walmart.com/ip/22217031?wmlspartner=wlpa&selectedSellerId=3&adid=22222222227016071111&wl0=&wl1=g&wl2=c&wl3=25284463476&wl4=&wl5=pla&wl6=50530064556&veh=sem
https://www.starmarinedepot.com/sierra-omc-3%2F8-fuel-connector.html?gclid=CLaa-6TntLoCFVRk7AodomQAFw

That way you can mix and match so that you can connect a tank with an Evinrude connector to a motor with a Mercury connector. Some people are using automotive fuel line from an auto parts store which would be a lot cheaper. Or you could buy one like this, and just switch the connector on the tank end to match the one that you have on your tank. https://www.academy.com/shop/pdp/attwood-mercury-fuel-line-kit/pid-600103

NOTE: All the links I've posted are just examples of what I'm trying to describe and not something that I'm saying is the style you need or that the quality is what you want.
 
[url=https://www.tinboats.net/forum/viewtopic.php?p=332830#p332830 said:
Canoeman » 23 Oct 2013, 18:12[/url]"]Personally for how cheap gas tanks are i wouldnt waste my time trying to get it clean.

Its not worth having one piece get hung up in yer carb...

IMHO

X2!

Post a pic of the connection on the engine, along with year/HP rating. You'll get a lot of advice that way.
 
filters are your friend and cheap, too.

Hook that thing up to electrolysis and let it go. Check the sacrificial anode every couple of days (last tank I did I let go for 4 days - completely clean of rust).
When clean slosh some oil around in side to prevent flash; fill it up and keep it full.
Put a filter between the priming bulb and the motor connection and/or put a small filter prior to or after the fuel pump. Good-2-go.

If you do this and still have problems with rust or something else getting to your carb you're jinxed and should be very careful with all things in life. :LOL2:
 
So I broke down and bought a new 6g plastic tank. Tank has an inline pressure regulator made my mercury. Also got a new fuel line assembly and swapped out the old merc style fitting to my new line. With it , I put a quick connect after the regulator so I can use the same tank for both motors by just switching out the fuel lines. $180 for the complete setup. Well worth it for a piece of mind. I'll work on the metal cans with different methods from above. Thanks all!!
 
$180 ! Thank you to the EPA
Guess I can go up a little on my old steel tanks when I sell them.
I bought a 1969 Evinrude 6hp in pristine condition and a 1960 Johnson 18hp in decent condition this weekend for $175. Guess everything is relative.......
 

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