Leaking fuel tank

[PANorth]

A few days ago we discovered diesel in the bilge of our E38. We removed the battery (forward of the fuel tank under the quarter birth) to find a slow-drip rate of flow coming from under the fuel tank. The rate is about 1/2 gallon a day, which is what we are removing from the bilge. We cleaned the tank a year or so ago while the boat was on the hard. There was no sign of corrosion at that time. The tank sat empty until a month or so ago when we were approaching splash time. We assume the leak is a fitting or a weld. She went back into the water a couple of weeks ago.

There are no visible leaks to be seen through the hatches to the tank. So we seem to need to cut into the bunk to see the nature of the leak. I started to remove the trim around the bunk but realized that the bed of the bunk was probably the first thing to go in. We would need to disassemble a good part of the cabin to get to the tank. I'm thinking that we should just cut through the bunk around the tank, removing just enough to see all sides of the tank. Then, assuming we don't need to remove the tank, we will screw support boards under and around the opening (there is probably a term for that but I don't know it) to attach the piece of wood we took out.

Has anyone had to deal with this? How did you approach it?

 

[Christian Williams]

I opened up the quarterberth lid to install inspection ports on the tank. The original top was glassed in, so a new top was later required.

Video below may help visualize the job.

If your tank is like mine, it would have to come out to be inspected and tested. Many of us have had to do that. Some tanks can be repaired, alternatively a new tank can be built.

If your 38 has the privacy surround, yeah, that would have to be disassembled.

E381 - "Thelonious II" -- Fuel Tank Inspection Ports -- Five-Minute Video

I use the engine to charge the batteries, and although there is solar capability on the new boat, I want the engine to run after rough weather has shaken the fuel tank like a rag doll and left arms, legs and little button eyes of ancient glop to...

ericsonyachts.org

 

[PANorth]

Yes, it has the privacy surround.

If the problem is a broken weld, I wonder if the tank can be filled with an inert gas and welded. ??

 

[PANorth]

The video is very helpful. It gives me a lot more confidence in opening up the bunk. I see there are benefits beyond the immediate need.
Thanks

 

[Prairie Schooner]

@PANorth Phil and Amanda,
Below you'll find more than you ever wanted to know about fuel tanks. In addition to Chris' excellent video above.
We replaced the tank in our 35-3 this past season.

- https://www.practical-sailor.com/systems-propulsion/diesel-engines/diesel-fuel-tank-replacement
- https://ericsonyachts.org/ie/threads/e35-3-replacing-fuel-tank.17731/#post-156979
- https://ericsonyachts.org/ie/threads/ericson-30-fuel-tank-replacement.18261/page-3
- https://ericsonyachts.org/ie/threads/fuel-tank-inspection-port-design-and-installation.13949/
testing + https://ericsonyachts.org/ie/threads/plastic-diesel-fuel-tanks-worrisome-outcome-for-tally-ho.20227/
- https://ericsonyachts.org/ie/threads/removal-of-fuel-tank-in-32-3.20272/
patch leaked + https://ericsonyachts.org/ie/threads/replacement-fuel-tank-for-38-200.16667/
E33 https://ericsonyachts.org/ie/threads/new-fuel-tank-ordered.20005/
Loren https://ericsonyachts.org/ie/threads/diesel-tank-replacement.6303/
- https://ericsonyachts.org/ie/threads/1986-38-200-fuel-tank-removal.19449/
E38 tank pics https://ericsonyachts.org/ie/threads/diesel-bug.19192/
- https://ericsonyachts.org/ie/threads/need-advice-please-on-aluminum-diesel-tank-repair.18542/
- https://ericsonyachts.org/ie/threads/need-advice-please-on-aluminum-diesel-tank-repair.18542/
ready-made ports https://ericsonyachts.org/ie/threads/inspection-ports-for-fuel-tanks.18789/
case studies https://goodoldboat.com/tankseasy-to-forget-too-important-to-dismiss/

Installation
good

surveyor advises https://www.yachtsurvey.com/fueltank.htm
ref to “ https://www.proboat.com/2010/03/strapping-it-down/
- https://www.thehulltruth.com/boating-forum/8061-best-way-secure-aluminum-fuel-tank.html
corrosion re: rubber https://www.sailnet.com/threads/rubber-galvanic-corrosion.40451/
corrosion re: rubber https://patents.google.com/patent/US5100733A/en
- https://www.powerandmotoryacht.com/maintenance/tips-on-replacing-the-fuel-tanks-on-your-boat
Not Neoprene https://www.thehulltruth.com/boating-forum/1157599-boat-fuel-tank-installation.html
point/counterpoint https://www.boatdesign.net/threads/proper-installation-of-aluminum-fuel-tanks.28605/
- https://stevedmarineconsulting.com/fuel-tank-installation/
corrosion prevention https://www.passagemaker.com/technical/tested-tankage
- http://fadelfacadedesign.blogspot.com/2012/08/aluminum-in-contact-with-other-materials.html

It was so much work to get our tank out that we opted to have a new aluminum tank made rather than repair. I didn't want to do it again. As I recall, it cost us $1500. A friend with an E31 cut sections out of his tank to create a cradle and had a flexible fuel cell fabricated. We looked into this, but it was far more expensive. It may be an option for you compared to removing all the woodwork. It's a royal PITA either way.

Good luck!
Jeff

 

[PANorth]

Thank you Jeff. I will start reading.

 

[vanilladuck]

Sharing my experience: earlier this year I found those all too familiar traces of pink in the bilge of my E32-3.. I didn't bother trying to repair the tank and instead ordered a new one fabricated. Definitely the pricier option, but I wanted the peace of mind the tank would not be a problem in the future (esp. with aspirations to sail offshore).

I worked with Jayson at Coastline Equipment in the tank department. They are located in Bellingham, WA - https://coastlinemarinetanks.com/

The tank came out great, although I have yet to install it. Some 38 year old 1/0awg battery cables were exposed when the tank was removed. So, I figured I would replace those first. And, then that led into rebuilding the core of the DC system because... Eh, nevermind, story for another thread/blog

 

[PANorth]

Thanks Bryan. We got the fuel out of the tank and cleaned up all the we could see (we know it will be showing up for a while). Then I put a few cups of water with green food coloring to see if the low point is the source. The green water showed up in the bilge. There is not obvious corrosion at this location, but it is clearly leaking. I am inclined to avoid taking out the tank by going with the fiberglass option mentioned in other threads on this topic. If that doesn't work, we'll go with removal and repair or replacement.

 

[vanilladuck]

Aye, the pinhole leaks which develop in these old tanks aren't always readily visible. I found several spots on my old tank which were weeping diesel.

I can understand your inclination to avoid removing the tank based on the amount of work it would take. Sounds like a reasonable stepwise approach

 

[Dave G.]

I am inclined to avoid taking out the tank by going with the fiberglass option mentioned in other threads on this topic.

Generally the corrosion occurs in the lowest point under the fuel pick. All the crud settles down low and eats away at the aluminum. I used epoxy(West System) and fiberglass to repair mine a couple of years back and so far so good. The hard parts were installing an access/inspection port & cleaning out the tank. It's definitely a viable alternative IMHO. The folks at West system were very helpful too with recommendations of product and techniques. Good luck and let us know how it goes.

 

[K2MSmith]

Generally the corrosion occurs in the lowest point under the fuel pick. All the crud settles down low and eats away at the aluminum. I used epoxy(West System) and fiberglass to repair mine a couple of years back and so far so good. The hard parts were installing an access/inspection port & cleaning out the tank. It's definitely a viable alternative IMHO. The folks at West system were very helpful too with recommendations of product and techniques. Good luck and let us know how it goes.

Interesting solution. I have a builder in SoCal who will make a new aluminum tank for me but I have to drive it down there ( 400 miles ) and have the boat offline while he’s making it . Once I get the tank out , if the corrosion is localized, maybe a glass / epoxy patch is a possibility. I already have an inspection port on mine .

 

[Frank Langer]

Interesting solution. I have a builder in SoCal who will make a new aluminum tank for me but I have to drive it down there ( 400 miles ) and have the boat offline while he’s making it . Once I get the tank out , if the corrosion is localized, maybe a glass / epoxy patch is a possibility. I already have an inspection port on mine .

That sounds like a good plan. Although some sailors on this site have been successful in applying an epoxy patch, I was told that epoxy will not adhere well to an area that has had diesel fuel on it, even with rigorous cleaning. That led me to buy a new tank for peace of mind and to avoid having to go through the arduous process to remove it again.
If you can make a patch work, it will save time and money. A tough decision!
Frank

 

[Christian Williams]

If I went to the trouble of getting the tank out, it would not be a tough decision for me.

Say, I wonder what a new 55-gallon diesel tank of 1/8th aluminum cost the builder back in 1984?

 

[Dave G.]

Once I get the tank out , if the corrosion is localized

Can you access the low point/pick up area from your inspection port ? If you can no need to pull the tank to make the repair. That being said you need to be able to be able to thoroughly clean inside and then sand the area for patching. Not sure where your tank is but mine is under the cockpit so some boat yoga was required

 

[K2MSmith]

Can you access the low point/pick up area from your inspection port ? If you can no need to pull the tank to make the repair. That being said you need to be able to be able to thoroughly clean inside and then sand the area for patching. Not sure where your tank is but mine is under the cockpit so some boat yoga was required

Fortunately the tank in my E33 looks accessible - a few wood pieces. The filler / vent hoses looks like the most difficult thing, unless I just cut it off ..there isn’t much room to pull them . Hopefully will see tomorrow. My electric extraction pump failed after 15 gallons , so I bought a giant hand pump ( 6L ) . Hoping to use this to change engine oil too .

 

[PANorth]

My tank is under the quarter birth. We already cut off the birth. Now I will expand the inspection port, a la Christian's video. Then it will be pretty easy to access the lowest spot in the tank where the leak seems to be. We already cleaned the tank, so a final cleaning for this purpose will be pretty easy. There have been enough people on this forum who tried this technique with good results that it's worth trying. My plan is to refill the tank five gallons at a time to verify that the leak is patched and help locate any other leaks. If it doesn't work we are not set back too far and at least we didn't needlessly remove the tank, which will require a lot of carpentry (my weakest skill).