Need some advise, little frustrated, some idiot stripped my gas tank threads.

[projo198]

Today I pulled my whole fuel system from my tank to the carb. I noticed the aluminum elbow screwed into the tank was fighting me, and when I got it off I discovered this mess!

I reprofiled what threads were left in the tube, but the tank threads are shot. I used pipe compound and tried to get it to go on but it was crooked as hell and leaked immediately.

To top everything off my tank is COMPLETELY FULL.

My only thoughts are draining the tank, drilling and tapping the tank hole and then using brass air fittings to reconstruct the tube.

Has anyone ever had this problem and found a solution?

 

[Boomyal]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

Did you chase the tank threads with a pipe thread tap? If the fitting went back in crooked, you must not have. You could always lower the fuel level in the tank and use Permatex Cold Weld Epoxy (I think it is fuel proof) to run it back in. It sets up pretty fast but takes 16 hours to cure. You may be able to wax the male part and back it out before the epoxy sets entirely. Then use some teflon tape with a fuel proof sealant when you run it back in.

A friend of mine used that stuff for a motorcycle oil drain plug and it worked well.

 

[projo198]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

The tank threads are pretty much shot. There was maybe 2 complete threads towards the bottom I tried to get a hold on, but it wasn't enough.

That's a good idea, I was considering using "liquid steel" putty, I have had success with that on vacuum lines and fittings. My plan was to cover the tube thread with it, mold it to the existing hole on the tank and slowly twist the pipe out before it fully cured, thus creating it's own threads. I don't think this would seal well though.

I think I have a better idea. I wen't to the home depot today and found a galvanized fitting that should fit my pick-up tube. I should be able to use a pipe-thread tap set and re-tap the tank for 3/4 inch, then use this adpater.

http://www.homedepot.com/Plumbing-P...&langId=-1&storeId=10051&superSkuId=202904823

I am also picking up a new pick-up tube today from Cabelas, becasue most of the threading is gone mine.

I wen't to a local boat shop and his only suggestion was to remove and replace the tank. I would have to cut up the whole deck for that!

What do you think?

 

[louiefl]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

Not sure how long galvanized steel would last, or if there is enough meat on the top of your tank to effectively tap. There is also the need to drill a larger hole (electric drill + gasoline vapor = boom!), capture the shavings (both driling and tapping). Maybe you could use an air-powered drill, though not sure how explosion prrof they are.

You might be able to find the reducer bushing in brass which might resist corrosion better than glavanized steel - temporarily, anyway. If you can somehow make this work temporarily, I think the long term fix is to use all the gas, flush it out to eliminate all gas vapors and weld a new metal plate to the top of the tank that could then be tapped for the pick up. Cheaper than cutting the sole open.

 

[projo198]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

Thanks. The part the pick-up tube screws into is actually a tab welded onto the top of the tank so it is thicker, should be plenty of aluminum to thread.

I will look for a brass substitute for the steel, that's a good idea. I do plan on welding on a new opening after the season, once I find someone that can weld aluminum and doesn't mind doing it inside the boat. I know a guy that used to build my custom fuel cells, I need to find his number.

I had planned on siphoning the tank before I started all this, but draining 21 gallons is going to suck. Since it is aluminum I am drilling and there shouldn't be any sparks where the bit meets the metal I am considering running a shop vac to suck up the shavings and covering the drill site with a towel. Do you think these 2 measures will be enough to suck away any vapor that could cause a danger?

 

[minuteman62-64]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

I've seen that same fitting in brass at Home Depot. In my Home Depot you do a 180 from the galvanized fittings and you are facing the brass fittings. Any Ace Hardware of similar should also have it in brass.

If you go the epoxy-mold route, Johnson's Paste Wax has worked well for me as a "mold release."

 

[MH Hawker]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

Their used to be a product called form a thread around that works real well.

 

[superbenk]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

Using a shop vac to suck away fuel vapors sounds like a terrible idea. That sounds a lot more adventurous than anything I'd try. I think you're better off making absolutely sure that tank is clear by draining it completely.

 

[nlain]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

Just seal the threads with pipe dope rated for gasoline and you should be good

 

[tpenfield]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

The shop vac will most likely lead to a fairly major explosion. So, you may want to avoid the shop vac or anything electrical for that matter.

With the tank installed in the boat, it would be best to drain off all the fuel (looks like you won't need to go to the gas station for a while) and then fill the tank with detergent & water. This will get rid of the fumes.

In terms of thread repair . . . if you can make the existing threads good again that would be best. If not . . . perhaps some sort of helix coil . . . I'm just not sure what would be best for aluminum. You will have to use a fuel-proof sealant on it, etc.

 

[projo198]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

I tried heli-coils, but they do not come in pipe threading. That would have been nice.

Here is waht I came up with. I wen't to Cabelas and bought a new pick-up tube, but discovered the fitting was much smaller. So I thhen went back to Home Depot, returned the galvanized steel fitting and replaced it with 2 brass fittings, pictures below. I think this will do the trick.

I also had to buy the tap made for 3/4 pipe threads, damn that was expensive. I am hoping to get this all installed this evening, I'll post pics if all goes well.

 

[nlain]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

When you go to tap that hole out, fill the tap with grease, it will help hold the filings so they don't drop into the tank.

 

[projo198]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

When you go to tap that hole out, fill the tap with grease, it will help hold the filings so they don't drop into the tank.

Great idea, thanks!

To whoever moved my thread thank-you. Sorry I wasn't sure exactly where it belonged.

 

[projo198]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

Ok I got this one fixed. First I had to remove the water pump so I could get a straight shot downward with the drill. Then I drained the tank by siphoning it through the boat's drain hole.

I had a 3/4 in brass fitting, a 3/4 in tap, so a 3/4 in drill bit should work, right? Not so much, it was WAY too small.

I ende up having to wallow out the hole with the drill until it was close to the right size, them finishing it with the tap. It took forever, but on the second try I got the tap to take bite and ended up with a good set of threads!

I rinsed the tank out and shop-vacuumed it dry. I'm letting it sit open tonight and tomorrow to fully dry out, and I will post a pic of how it looks all done.

One thing I need to know. Will this stuff I bought at Ace True Value withstand gasoline? It says it is good for gas piping but I don't know about gasoline.

Thanks!

 

[tpenfield]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

That is a no-go on the stuff from Ace Hardware. You will need to stop by the auto parts store and get "Permatex #3 aviation form-a-gasket" which is fuel and solvent resistant.

 

[delirious]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

Not sure how long galvanized steel would last, or if there is enough meat on the top of your tank to effectively tap. There is also the need to drill a larger hole (electric drill + gasoline vapor = boom!), capture the shavings (both driling and tapping). Maybe you could use an air-powered drill, though not sure how explosion prrof they are.

You might be able to find the reducer bushing in brass which might resist corrosion better than glavanized steel - temporarily, anyway. If you can somehow make this work temporarily, I think the long term fix is to use all the gas, flush it out to eliminate all gas vapors and weld a new metal plate to the top of the tank that could then be tapped for the pick up. Cheaper than cutting the sole open.

you have to steam a used tank for an extended period b4 welding or KABLOOIE, working (drilling etc) with a FULL tank is SAFER than an EMPTY tank.

 

[Home Cookin']

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

I lot of good info here; I'll add some thoughts. I've been dealnig with some tank issues, too.

Don't use teflon tape; gas dissolves it and you get goo in your system. Probably true of other products.

Not a good idea to mix metals, esp in salt water. But if you do, make part of your annual maintenance removing and reinstalling.

The seal for the tube fitting to the tank does not have to be absolutely air tight, unlike the seals along the fuel path so you don't get an airleak. But you want to seal well enough that you don't get gas splashed out the fitting, or rain water dripping in. So for repair purposes you can try many less-than-perfect alternatives, including a soft seal you check/replace periodically.

 

[louiefl]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

you have to steam a used tank for an extended period b4 welding or KABLOOIE, working (drilling etc) with a FULL tank is SAFER than an EMPTY tank.

I would imagine that welding a new aluminum plate on top of a tank wouldn't be done by the OP and whoever was doing the work would use the appropriate precautions. Thanks for the clarification. I was paranoid about swapping out my sending unit (5 screws by hand) thinking one false move and my wife would be cashing in that insurance policy.

By the way, the oversize bushing appears to be 3/4-14 NPT as you figured out by getting the right tap. The appropriate drill for this is 29/32" or 0.906" - you must have had some serious hogging out to do. Google "NPT tap drill" for all the rest of the sizes.

Glad you got it fixed. Since Aluminum is a more active metal in the galvanic sereis than brass, the aluminum threads (tank and pickup) will want to give up material before the brass fitting. What you want to do in the long term for a permanent fix is get a "aluminum 3/8" NPT female x 3/4" NPT male reducer bushing"; something like this:

http://secure.chassisshop.com/partdetail/991208/

 

[projo198]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

I would imagine that welding a new aluminum plate on top of a tank wouldn't be done by the OP and whoever was doing the work would use the appropriate precautions. Thanks for the clarification. I was paranoid about swapping out my sending unit (5 screws by hand) thinking one false move and my wife would be cashing in that insurance policy.

By the way, the oversize bushing appears to be 3/4-14 NPT as you figured out by getting the right tap. The appropriate drill for this is 29/32" or 0.906" - you must have had some serious hogging out to do. Google "NPT tap drill" for all the rest of the sizes.

Glad you got it fixed. Since Aluminum is a more active metal in the galvanic sereis than brass, the aluminum threads (tank and pickup) will want to give up material before the brass fitting. What you want to do in the long term for a permanent fix is get a "aluminum 3/8" NPT female x 3/4" NPT male reducer bushing"; something like this:

http://secure.chassisshop.com/partdetail/991208/

Ok gotcha. I figured someone somewhere made an aluminum fitting. Thanks.

Yes it was a real PAIN getting that hole big enough, and I am sure the fact that it wasnt' a perfect circle contributed to the difficulties I had getting the tap to take right. Thanks for the reference. I am not sure where I would find a drill bit that big anyway, the largest I was finding was 3/4.

No I don't plan on welding the tank myself, I am not set up to weld aluminum. But with the aluminum fitting mentioned above would this not be pretty much a permanent fix, as long as it doesn't leak?

 

[minuteman62-64]

Re: Need some advise, little frustrated, some idiot stripped my gas tank threads.

Yes it was a real PAIN getting that hole big enough, and I am sure the fact that it wasnt' a perfect circle contributed to the difficulties I had getting the tap to take right. Thanks for the reference. I am not sure where I would find a drill bit that big anyway, the largest I was finding was 3/4.

A tapered reamer is often used when prepping a hold for tapered pipe threads. But, reaming 3/4" hole out to almost 1" would take a lot of twisting