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ChicagoNewport27 03-09-2008 06:32 AM

Replacing my fuel tank this Spring, and need your sage advice.
I'm going to be pulling the old leaking [gasoline] fuel tank from my Newport 27, and will be replacing it with a new tank. The new tank will just be an off-the-shelf tempo marine polyethylene tank, probably. I've yet to decide on the size and shape of the new tank, as that'll really depend on what size and shape will fit through the lazarette hatch.

I've been searching here on Sailnet, and elsewhere, for advise on how to drain, remove, and replace fuel tanks. So, first off, any advice you can offer would be much appreciated.
  1. Whats the easiest (and safest) way to remove nearly 20 gallons of three year-old unleaded gasoline from a leaky aluminum tank?
  2. What is the easiest way to remove the old tank, especially when it is likely too large to be hoisted through the lazarette hatch?
  3. If I need to cut up the tank, how do I ensure all the gasoline is out of it first (it has no inspection ports)? What is a good tool to cut up an aluminum tank (I couldnt begin to guess how thick it is)?
  4. Will I need an engine hoist or some kind of tackle attached to the boom to pull the tank (I'm imagining its pretty heavy, even when empty)
  5. What size tank (or tanks, plural) should I consider to buy to replace my 25 gallon aluminum tank? I feel 25 gallons is overkill for a 27' ft coastal cruiser that is used only on the occasional weekend or overnight trip on Lake Michigan. The engine is an Atomic 4, and has to-date only been used when motoring in and out of the harbor.
  6. I also feel that aluminum is overkill, but feel free to set me straight. Is it false economy to buy a plastic tank to replace an aluminum tank?
  7. Should I buy two smaller tanks to replace the one large tank, and if so, how do I plumb them together? Some kind of tank selector valve? That way I could have a small day-use tank, and a bigger tank in case I want to pack extra fuel for a longer trip.
  8. What am I forgetting?
  9. Have any of you seen any websites or sailing blogs with step-by-step pictures of fuel tank replacements? A picture is worth a thousand words.

While doing a Google search on the subject, I came across these guys who advocate removing old fuel tanks in a much different manner; instead of pulling the old tank out topside (through hatches, etc), they just cut the hull around the tank, drop the plug including the tank, replace the tank atop the plug, reinsert the plug, then glass it all back together again. Whoa!


What do you guys think about that method?!

Thanks in advance!
- Ken

sailingdog 03-09-2008 09:04 AM

You need a small pump to pull the fuel out. They sell small piston pumps at the hardware store that can do this.

Cutting the tank apart is probably the only way to get the tank out, since it is very likely that the tank was installed before the hull and deck were joined.

The pieces of the cut up tank shouldn't be all that heavy, so you shouldn't need a crane or hoist to pull them out.

As to how large a tank to put in... put in at least a 12 gallon tank. That gives you enough fuel capacity if you should decide to take a longer trip, and is large enough that you don't have to continually refill the tank.

Since these tanks are mounted in the lazarette, I am hoping that you're planning on using a deck fill to fill them rather than trying to muck around with pouring gas into a tank in the lazarette itself.

I like the idea of having two tanks and think it is a good one, but it will require a bit more work since, you'll need to add a second fuel deck fill and vent line, as well as a diverter valve for the fuel tanks.

Modern plastic tanks are perfectly serviceable and will last a fairly long time provided the tank is securely mounted, well supported, and protected from chafe and UV.

Cutting the tank out through the hull strikes me as good for the boat yard, bad for you and the structural integrity of the boat. Even glassing the plug back in from both sides would probably leave the boat weaker than it was before doing so, since the strength of fiberglass depends on long continuous fibers...and cutting a hole in the hull destroys their continuity.

As for actually cutting the tank apart.. Hmm... That's always a problem, especially making sure that all of the gasoline is out. If you're going to be cutting the tank apart in the end, cutting a large inspection port into the top of it could be done using hand tools and allow you to make sure the tank is empty and vent any remaining gasoline vapors out of the tank.

Once the tank is empty, cutting it apart with a sawzall would be relatively easy. You'd proably want to cut the most accessible parts of the tank up and then pull the rest in one large piece if possible. You'll need to remove whatever fasteners are holding the tank to the hull. I'm guessing that it is bolted or screwed to the hull in some way.

craigtoo 03-09-2008 11:56 AM

With regard to cutting the tank out.

Obviously you want to make sure that the tank has no more gas fumes.

After pumping, I would recommend filling the tank again with water about 3/4 full, let it settle for an hour or so. Since gasoline is less dense than water it should "float" on top. Re drain the tank with your hand pump, but be sure to pump out from the top. Skimming the pump along the surface. Does that make sense?

Rinse and repeat.


ChicagoNewport27 03-09-2008 12:47 PM

Good advice guys. Thanks! After pumping out all the gas, it does sound like a good idea to refill the tank with water to get any remaining fuel out.

Should I fill the tank with water that has some kind of soap mixture added to it (I'm thinking good ol Dawn), or other additive to neutralize whatever gas remains?

craigtoo 03-09-2008 05:24 PM

Disclaimer.. I've never done what you're about to do.

I'm not aware of anything that can "neutralize" gas.

That being said.... repeated rinsing with Dawn would probably be a good idea.

If you're using a sawzall etc. there will be sparks. Make sure that you've rinsed several times and allowed any and all fumes to vent before starting this. Nothing worse than a fire in a confined space. Be very... very .... very careful.

Vent Vent Vent.
Rinse Rinse Rinse.

Maybe even rinse to overflow a few times. Capture what flows over as it may have gasoline in it.

Have fire extinguisher handy.
Don't work alone.

Think Safety.


sailingfool 03-09-2008 05:37 PM

54 Attachment(s)
I would expect that a plastic tank would not pass a survey, even if you properly secure and vent it...have we ever seen a internal plastic tank in a new boat...not that I know of. Maybe our resident surveyor can comment.

If my suspicion is correct, you are likely to find that you end up spending the money to properly install a new alu trank when the next buyer can't get financing or insurance on your may have trouble with your insurance.

Gasoline is dangerous, probably not an area for the handyman to have a learning experience.

just my opinion.

Freesail99 03-09-2008 05:39 PM

I don't think this is a good idea. When I was 17, I had a leaking gas tank. I removed it from my car, drain it and rinsed it out with water at least 15 times. I planned on welding the hole in the tank. I touched the torch to the tank and I launched it at least 50 feet in the air. It crashed on the road crushing part of it. I ended up doing to the junk yard and getting one for $5.

craigtoo 03-09-2008 05:56 PM


Originally Posted by Freesail99 (Post 279869)
I don't think this is a good idea. When I was 17, I had a leaking gas tank. I removed it from my car, drain it and rinsed it out with water at least 15 times. I planned on welding the hole in the tank. I touched the torch to the tank and I launched it at least 50 feet in the air. It crashed on the road crushing part of it. I ended up doing to the junk yard and getting one for $5.

Well...that does it for me.

Based on the testimonial above....I wouldn't cut the tank. Gasoline is just too dangerous.

sailingdog 03-09-2008 06:58 PM

Dawn or any good detergent or alcohol will act as an emulsifier and allow the gasoline to mix with the water.

If in doubt, get some dry ice and drop it in the tank and let it sublimate. It will force most of the oxygen out of the tank... and reduce the risk of explosion. However, try not to use too much Dry Ice since the CO2 concentration in the boat might go up and put you at risk too. :)

timday5 06-04-2008 05:06 PM

I just cut my aluminum tank out of my boat and didn't blow up. The tank was too large to pull out through the lazerette hatch.

I used a special hand saw ($10) I bought at Lowes that allows you to use sawzall blades. Used a 14 Tooth Per Inch sawzall blade. If I had to do this again, I would have used a longer blade (more efficient cutting, ie, less back and forth).

First, I had to cut away the fiberglass from the aluminum tabs that held the tank in.

Second, I had to make three long cuts (18 - 20") in order to cut a corner of the tank off (it was an odd shape) in order to get the tank down to a size that could be pulled through the hatch. It took an afternoon.

If you do fill the tank with water, remember that legally (I'm pretty sure) you have to dispose of the water as hazmat (like the gas). I would not want to risk my life using a sawzall, even after rinsing the tank out with water. I just don't know enough about how to make sure all the fumes are gone prior to using a heat and spark generating device on the tank.

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