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Thread: Flush inboard fuel tank without removing it???

  1. #1
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    Default Flush inboard fuel tank without removing it???

    I have a conundrum...I would like to flush my boats fuel tank but I don't have the ability to remove it from my 1984 Bayllner 2450 Ciera. I have removed as much fuel as possible using an auxiliary fuel pump but of course there is still some remaining at the bottom with a decent amount of what I believe is scale and dirt sediment. I really want to remove all of the sediment as I an because I believe it is the culprit to some boating issue I experienced this summer with me losing power in choppy waves and me having to shut down my boat to let the dirt drain from the pick-up tube and the restart and run a bit more until it lose power again. I believe it to be due to the fuel because I checked my Racor fuel filter when I was experience the loss of power and open up the bottom drain plug and no fuel came out leading me to believe something had plugged off the pick-up tube. When I made it back to dry land I did find scale on the pick-up tube filer and in the pick-up tube itself.

    After all of that I figured I would flush my fuel tank as best a possible to get rid of all the debris I could. Which leads me to my original question. Does anyone have any creative ideas? Should I drill a hole in the fiberglass covering my tank and then into the bottom of my stainless steel tank as a drain? Are there any companies that would perform a good flush for me? The biggest opening I have on the top of my tank is about 1.5" in diameter so it is a bit difficult for me to get much done from the top with my remedial skills and tools

    I am open to any and all suggestions. Thanks in advance

  2. #2
    Moderator bkmail's Avatar
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    Shop vac with a 1" or 1.25" hose duct taped to the end of your normal shop vac hose. Ie....neck it down with something and work it all over in there to get any residual trash removed. If you use a new filter on the vac you could cut it open afterward and see how much was removed.
    Obviously this tank needs to be well vented/dry and free from any gas residue to avoid a spark from the shop vac igniting the vapors. You could flush the tank with water a couple times to help prevent this??
    BK

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    Premium Member kasilofchrisn's Avatar
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    Basically what I did on mine was what BK suggested. I was able to pump most of my old gas into a portable tank my dad has that has its own filter on it.
    This allowed my dad to use the gas for his tractor etc and the filter should catch the particulate.
    On my tank I was able to remove the fuel tank level float system giving me a 1.5" hole at the back of the tank that I could access with the engine hatch open.
    I jacked the front up high enough so everything ran to the back.
    Worked good for me.
    I am guessing you would also have a removable level indicating float assembly that is accessible from the top. Mine had 6 screws a ground wire and another wire that was easily removed. You may need a new gasket or some silicone when you go back together.
    "The closer I get to nature the farther I am from idiots"

    "Fishing and Hunting are only an addiction if you're trying to quit"

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    Member cormit's Avatar
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    Think twice before sticking a shop vac into that fuel tank and don't drill any drain holes in the bottom. Flushing the tank with water to make it explosion proof is not adequate either.

    Coast Guard and ABYC standards don't permit any fittings for draining or fuel supply that are below the highest point of fuel in a tank intended for gasoline.

    Like Kasilochrisn said ..... if you have a fuel gage in the top of the tank ...... you could remove that and have a reasonable size hole to work through. You could use a rose gun (hand vacuum gun) to remove all the fuel, then with a diesel dampened rag on a stick, you could slowly mop out the bottom of the tank and any debris that has collected there.

    If you do something to ignite the fuel vapor in the tank ...... you won't need to worry about the other problems.

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    Member sayak's Avatar
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    X3. That is what I did on my Olympic I/O down in Homer; I used the float hole as access. I was able to use a 10' length of stiff garden hose with a short piece of galvanized pipe nipple on the end (for weight), pushed it all the way to the back of the tank, and sucked the tank dry that way. After I got out everything, I put a whole bunch of HEET in the tank and sucked it out again. There may have been some left over, but not much and it never caused me problems after that. I would definitely avoid a vac. and adding water is adding insult to injury IMO.

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    Moderator bkmail's Avatar
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    BigDC,
    There you have it, wiser men than I have given you better knowledge on the subject.
    Let us know how you did it and how it worked for ya.
    BK

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    I drain a lot of gas tanks in my time and after I finish typing an answer, I waited until I saw what others has posted. The reason was gasoline fume can kill you, if you don't take precaution to make sure you doing thing right there is no 2nd chance. When you said you have remedial skills that scared me.

    If you decide to do it your self, spray everything down with water, shop vac, holes, fuel tank, etc to prevent static. Make sure the boat/fuel tank is grounded to earth ground. Do not have the container your going to put the old fuel in next to any motor like a shop vac. It was mention (You may need a new gasket or some silicone when you go back together.) gasoline eats silicone. I would not recommend using silicone.

    Your boat is 29 years old there is a good chance your fuel tank have corrosion causing pin holes this would be a good time to have it presser tested. I think your fuel tank is aluminum not S.S.

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    Moderator bkmail's Avatar
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    Big DC,
    MacGyver brought up a good point that I have experience with. I had an 84 bayliner explorer that developed a gas smell in the shop one day, just sitting there. Next day it had a couple drops of gasoline on the floor that came from the bilge. The following day I left a bucket under it and it had a couple cups of gasoline in there.
    It turned out the tank had pinhole leaks on the bottom that finally ate all the way through as MacGyver mentioned. I had CAC Plastics in Wasilla cut the deck open to access the tank. Greatland welding cut off the bottom of the tank and welded a new floor in it. CAC did a fine job glassing the deck again but I made it removable with stainless screws and sealant in the event I had to ever access the tank again.
    You might be in the same situation and I encourage you to do a pressure test as well so you are not on the water when it decides to weep leaving you in a very dangerous situation with raw gas in the bilge.
    BK

  9. #9

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    Does anyone know of a good outfit who deals with tanks (checks them out, fixes leaks and/or fabricates new tanks) in the Anchorage area?

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    Heavy Weather Boats 349-4325

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    Member sayak's Avatar
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    Boat owners either have a lot of money to spare, or don't, and sometimes those who don't have older boats which they work to keep alive. If I was confronted with an expensive tank job on an older boat, I would think seriously about tearing it out and using a cheaper solution, such as a couple of plastic ones of the 12-18 gallon range plumbed together. Even if I had to raise my floor up a bit to acommadate them, I would potentially be saving lots of $$$ and would have the luxury of pulling those tanks out when I wanted to... like every couple years.

    The tank I had in my Olympic was galvanized steel, BTW, and I didn't replace it, but I would now if I still had it. I would also yank out the outdrive and the space-robbing engine and go outboard all the way. I hate I/Os.

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    Thanks everyone for all the advice. I was very cautious removing the fuel. I utilized the existing tupbing right after my racor, without opening the tank, to hook my auxiliary pump up to with a long length of fuel line and then another long length of fuel line down over the side of my boat to my plastic fuel barrels located on the ground. After the majority of the fuel was pumped out I then got the rest through the float hole using the same fuel line and a plastic rod as a guide.

    Now what I have left is just the debris at the bottom of the tank and no more fuel. It will try the diesel dampened rag to see what I can get out for debris. I stuck a small endoscope camera into the tank to see what was in the bottom and there was definately debris in the bottom that I would very much like to get out in hopes that it will help to solve my issue. I have not seen any signs of pinhole leaks or fuel in my bilge so I dont think that pinholes are an issue for me curently. I dont have the funds to remove the current tank and redo my decking as that would require me to remove the engine as well and my pockets just are not that deep

    Any other ideas besides the dampened rag or adding more fuel and tipping the boat to suck it out of the tank?

  13. #13

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    You could get a piece of plastic pipe and tape it on your vacuum cleaner if you have all of the fuel out ,just make sure that the vacuum is out in the fresh air. If you have small amount of gas still get some cotton rags and fasten on a piece of wire and keep working it around until you have the fuel out of the tank ,remove the rag and squeeze out into a container and repeat.

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    I have cleaned gas tanks of dirt and other junk by putting in 10 gal diesel and pumping it through a Rocor filter with a fuel transfer pump sucking from the lowest point of the tank washing with the inside of the tank with the discharge hose. I may take some time. After done with one tank use the same diesel in the other tank if you have two tanks if not pump it out add gas and back to fishing.

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    Member cormit's Avatar
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    Quote Originally Posted by Big Bend View Post
    You could get a piece of plastic pipe and tape it on your vacuum cleaner if you have all of the fuel out ,just make sure that the vacuum is out in the fresh air. If you have small amount of gas still get some cotton rags and fasten on a piece of wire and keep working it around until you have the fuel out of the tank ,remove the rag and squeeze out into a container and repeat.
    It is not safe to use a vacuum cleaner of any kind with a fuel tank that was ever used for gas ...... even if all the fuel is removed. I'm sure there are plenty that will say they have done this and got away with it ...... it's still a bag idea. It takes very little gas vapor with the right combination of O2 to be highly ignitable. Even if the vac is outside ...... if it ignited ..... it could likely travel through the hose back to the tank.

    If you've ever been around a gas tank that exploded ....... it makes a heck of an impression.

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