Finding Fuel Tank Pinholes

Photo Bug · Jan 18, 2011

Yes there is an easy way. Use corks to plug up everything but the main filler. Pore some dishwashing liquid the tank. Fill it with water. Bubbles will start coming out of the pin holes. Best Idea? Most bigger cities have companies that will repair tanks. find them and take the tank to them and let them do there thing. You will be suprised how cheap it is to let them do it.

larryw · Jan 18, 2011

Duct tape all the openings with the outlet from your dink footpump in one of them. Pump as high as the pump will provide. Paint a dishwashing solution all over the tank. Bubbles will show leaks.

petersea · Jan 18, 2011

robertsapp said:
I pulled my aluminum fuel tank to clean it, and discovered a small amount of diesel fuel sitting underneath it. Maybe a tablespoon or so. We've had a diesel odor onboard since we bought the boat, so that could be the source. The tank has a flat bottom, and sat on some rubber strips around the perimeter about 1/8 inch thick and about an inch wide that I assume were there to keep the bottom of the tank off the fiberglass shelf it sat on. There is a brown stain on the side of the tank that starts below the fuel supply and return lines, which tells me that it's possible I had a small return line leak, and the fuel was dribbling down the side of the tank and getting underneath. Everything is 15 years old and the hoses looked pretty ugly wihen I took the hose clamps off. I want to be sure before I spend time cleaning and resintalling the tank that it doesn't have a pinhole leak. There are five penetrations in the tank - the fuel fill, vent line, supply and return lines, and the hole where the level sender goes, which I removed to suction the fuel out of the tank prior to removing it. Is there an easy way to test the tank to see if it has a tiny leak of some kind? I searched on 'fuel tank leak' and 'aluminum fuel tank' but couldn't really find anything that helped.

Ok here is my take on this if you have pinholes most likely the tanks is shot as it will have weak/soft areas and you will be better off replacing tank. I thought my 336 had a "plastic" not aluminum so I was surprised to hear you had that type. At 15 years old it might be better to replace a aluminum tank due to age as well especially if it has a pinhole or pinholes If my memory serves my correctly it is about a 30 gallon tank and unless doing alot of cruising is more then you will need and could be replaced with a smaller "plastic" tank (this will also insure you have reasonably "fresh" fuel)
If it it no more then a return line fuel leak you could replace the fuel lines and any fitting that may be questionable. If none of the other method work to find/check for pinhole use a flashlight from inside the tank to see if you can see light "pass thru" the tank wall.(do in the dark) If all methods fail a tank repair shop or tank builder should be able to inspect and pressure check your tank for you .

Good Luck !

Don12364 · Jan 19, 2011

My Experience

My aluminium tank in the previous boat was above and abaft of the engine, so to remove it the engine would have needed to come out first. Unbeknown to me the stern gland used to throw a very fine spray of seawater upwards on to the underside of the tank. It was a Deep Sea Seals carbon seal face contact type. In time the tank developed pin holes and I was desperate. The alternative was to take a jig saw to the cockpit sole and I didn't see how I was ever going to make the repair strong enough.
Enough of the terror story!
As a quick and simple fix (so we could race on the weekend!) I made up some quick setting resin, lightly wire brushed the under surface of the tank in situ, very quickly degreased with acetone and slapped on a coat of the quick set resin. Then I added several layers of fibreglass, making sure it was all very well saturated. I only did the bottom of the tank, working upside down over the engine in a very restricted space
Frankly I did not expect it to succeed - but the alternative was less palatable and would have to be done in any case if the quick fix did not work.

To my amazement it worked perfectly so I left it. A further 14 years later I eventually sold the boat (after pointing out my fix to the new owner.) I see the boat from time to time and the fix is now beyond its 21st birthday and, I believe, is better than new.
So we live and learn.

RichH · Jan 19, 2011

Most metal fuel tanks can easily be relined with epoxy fiberglass - essentially you build a new tank inside the old using the old tank as a form for the new. For large tanks this includes the baffles that are necessary to retard fluid impact.

The tops can be cut and large 'sister flanges' applied using studded closures. The only real requirement is that all 'dirt', oil and other contaminants must be thoroughly removed ... including the cracks and pin holes.
The old tank internals can be sand blasted or severely disc sanded to provide 'tooth' for the new fiberglass lining. the tank internals MUST be properly prepared as any leak or communication between the old tank surfaces and the new fiberglass would accelerate corrosion if there is leakage between the new fiberglass and the old tank metal material. Industrial 'degreasers' are used to extract any 'oil' inside 'welding faults' or weld scars / laps. Sealing of the sister flanges can be accomodated by using industrial supply pre-adhesive reinforced BUNA or Neoprene strip + fuel compatible caulk. I use 12 oz. fiberglass bi-axial cloth overlaid onto 4" wide strips that overlay each weld affected area of the old tank.

The pic. shows a 100+ gallon black iron tank 're-build' that I did about 8 years (about 25,000 nM) ago. Repair cost (~2003) was ~$125, time to repair - approx 30 hrs. This particular tank was re-built /re-lined 'in-place'.

shemandr · Jan 19, 2011

Replace it. 30 hours labor? What does that cost? It will be a great comfort to a buyer that you spent 30 hours on this repair of a worn out item and he will probably cite you as the "PO" on one of these forums. If you don't have to hack the boat up to get it out just get a new one!
Sorry but winter is testing my patience.

petersea · Jan 19, 2011

shemandr said:
Replace it. 30 hours labor? What does that cost? It will be a great comfort to a buyer that you spent 30 hours on this repair of a worn out item and he will probably cite you as the "PO" on one of these forums. If you don't have to hack the boat up to get it out just get a new one!
Sorry but winter is testing my patience.

Yikes 30 hours of labor ! ! At todays yard rates this equates to $2000 or $3000 of labor ! ! Plus materials $3125 repair ! ! New tanks with remove and replace labor is way way less the that ! ! And when you go to sell it more then likely a surveyor would beat you up on that type of repair and you would have to pay the repair cost to replace the tank anyway ! Sorry I still think if it is the tank replace it ! !

higgs · Jan 19, 2011

Get on the net and find a company that rebuilds tanks. They use epoxy and will guarantee the tank for life. Price is not bad. I did this to a a steel tank in my Irwin 32 and was completely satisfied.

RichH · Jan 19, 2011

petersea said:
Yikes 30 hours of labor ! ! At todays yard rates this equates to $2000 or $3000 of labor ! ! Plus materials $3125 repair ! ! New tanks with remove and replace labor is way way less the that ! ! And when you go to sell it more then likely a surveyor would beat you up on that type of repair and you would have to pay the repair cost to replace the tank anyway ! Sorry I still think if it is the tank replace it ! !

Let me attempt to tamp down the apparent hysteria by stating that this was a DIY job and done with a leisurely attitude. Total time included prep, emptying of the contents, disconnection, cutting, cleaning, glassing, etc. etc. etc. Total materials cost was $125 for LARGE 100 gallon tank, and the time spent was to carefully & accurately do the repair/restoration, not the typical overpriced slop-job done by a yard.

My time is 'free' and I therefore apologize to those who have no recourse, knowledge nor inclination to do their own 'work' but rather must hire others to do such.
;-)

RichH · Jan 20, 2011

Simple analysis
- Most pin holes that develop in metal tanks will be primarily along any weld areas / seams; due to improper/faulty welding or developed cracks in the 'bending', etc. When in doubt, simply tape absorbent paper towel strips to the weld seams and watch for transfer of oil RED DYE into the absorbent paper.

Since your tank is already out, just orient the weld seam/bend to the bottom and put in a bit of DYED oil to cover the seam, etc.

Another method is to simply take the tank to a welder who specializes in aluminum, tell him that you are 'suspicious' that the tank is beginning to leak and simply have him/her visually inspect the tank. A well practiced welder can quickly spot improper welds, weld laps, gas holes, etc. and may/can use special dye penetrants to further exam the tank ... the fix then is simple and will only cost a few $$. Ask him/her 'how much' before you commit.
;-)

higgs · Jan 20, 2011

Reconditioning the tank is not that expensive. If it is already out it is a no brainer.

kendall · Jan 21, 2011

RichH said:
the time spent was to carefully & accurately do the repair/restoration, not the typical overpriced slop-job done by a yard.

My time is 'free' and I therefore apologize to those who have no recourse, knowledge nor inclination to do their own 'work' but rather must hire others to do such.
;-)

I like RichH's attitude, it's the same as mine.

I get in arguments all the time because someone comes up and says "it's cheaper to pay someone to do it" or "my time's too valuable" most go home and watch TV, I've been searching to no avail for over 40 years to learn how to get paid for TV time.......

Decent way to find a leak, is to wash then paint the tank, leaks will wash off the paint.

The best emergency sealer I've found is 'seal-all', it works great and will seal leaks in gas water, and oil tanks while the fluid is still dripping out, no need for 'clean, dry, oil free' surface which is what makes most 'emergency' sealers all but useless in a real emergency.
(If I have time to drain, wash, dry, patch, and refill, why would I use an emergency patch?)

Winkfish · Jan 21, 2011

kendall said:
"my time's too valuable" most go home and watch TV

I'd much rather piddle around doing boat maintenance stuff than watch the trash that's on TV. However, I'd much rather spend time with my wife and son (and actually use my boat) than piddle around doing boat maintenance stuff.

Now, if they both get into piddling around doing boat maintenance stuff, I'll be a happy(er) man.

Ray Bowles · Jan 21, 2011

A interesting fact that is almost to strange to believe is that a gas leak from a gas tank can be sealed in the field by rubbing over the leak/crack with a bar of soap. I originally heard it had to be Ivory Soap but after hitting a rock 100 miles from any filling station my worst fear came true. We had bent the tank on our Dodge car and a leak was coming from the crease the rock made. We only had a bar of regular hand soap so I tried rubbing it into the leak and it stopped. We were camping so when we got out of the hills it was still dry. We drove it home 350 miles and drove it another 300 miles before a real repair. The leak was dripping about a drop every 2 seconds. I would stay out of the water though.
I don't know about deisel but it should also work there. It's worth a try in a pinch.
Ray