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Repair to fuel tank: '87 E34

sailingdeacon

Member III
The diesel fuel tank in my 1987 E34 developed a small hole in the lowest part of the tank - forward end, just at the lower v part. I poked it an expanded it to about 1/8" or smaller. I cleaned the tank and it looks good from inside, as I peer in.

Can a new tank be bought today? What about repair? From a professional aluminum tank welder? Patch with marine epoxy?

I have the dimensions but the tank has very exacting requirements.
 

mark reed

Member III
I have the same problem with the tank on my '87 E38. I pulled it out and took it to a local welder. He is very confident that he can repair the tank, which will be much cheaper than fabricating an entire new one (~$200 vs ~$900). I'm also having him put in inspection ports so that the tank can be cleaned more easily in the future. My only question at this point is what can I do in terms of re-installing the tank that will minimize the chance that this will happen again. We already have a dripless shaft seal.
 

treilley

Sustaining Partner
Same problem on my '85 35. PO had it welded. I installed an inspection port last year. I believe this is caused by condensation collecting at the lowest point on the outside of the tank and slowly eating away at the aluminum. Getting the tank off the liner can help. I think that a leaky cockpit scupper was also contributing to the wetness.

I replaced my cabin sole last year also but know this tank will leak again so I would like to have one fabricated from plastic. I had a custom holding tank made by a company in RI a few years back called CC Tech. I gave them a detailed drawing and they welded it togther and shipped it to me all for about $200. I will likely give them a call when it is time to do it. I will also downsize the tank a bit at the one end so it will fit though the companionway. The existing tank needs the teak trim removed to get it through.

CC Tech gave me a volume discount because a few other Pearson owners liked my design.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Before changing from metal to a plastic fuel tank, be sure to check with your ins. company and also with the applicable parts of the ABYC book.
Loren
 

sailingdeacon

Member III
Local marine folks have given me these ideas in decreasing order of preference:
1. Search for OEM poly tank replacements (not fiberglass) since the tank has no baffles.
2. Lab Metal repair kit for aluminum http://www.neverseezproducts.com/labmetal.htm
3. Red Hand by Interlux. an older product but sworn by many.
4. JB weld
5. Marine tex

By the way, I now see another hole and the area of concern is probably 1.5" square.
 

u079721

Contributing Partner
Stupid idea....

I once saw a demonstration of the plastic spray on material used to coat pick up truck beds. The stuff sticks like grim death, and is amazingly durable. The point of the demonstration was to try and get people to think up other uses for it.

Well...what about coating the outside of an aluminum fuel tank before you re-install it? It should at least do away with the exterior corrosion issues we all hear about.

Why don't one of you try it and report back to us in say ten years?
 

Tom Metzger

Sustaining Partner
Go for it, but...

I've always been a big advocate of stupid ideas, but I think that ten years is too soon for the report. I also question putting the coating on the outside of the tank. I am more inclined to believe that the problem is water and other crap inside the tank. On the E-34 in question the tank is supported from above, not below.

On my previous boat I got 16 years out of the steel tank. I was hoping to get much, much better life from the aluminum.
 

Randy Rutledge

Sustaining Member
The Aluminum tank on my 1978 E29 had a spot corroded through at the tip of the pickup tube. The cause was water in the fuel a copper pickup tube and the aluminum creates battery and the aluminum lost the battle. I posted a thread with pictures a few months ago.

I feel that first keep water out of the tank (Impossible) second shorten the pickup by about ½ inch.

I had to cut the deep part off the tank to get it out of the boat therefore I had a plate welded over the hole creating a flat section at the sump rather than a V at the front inboard corner.
 

sailingdeacon

Member III
Randy, I think I have the same problem as you did. See the two closeup photos. However the copper pickup tube is already 1" above the failing location, so I doubt raising it further would help. See photos. The two holes are actually very small, and what seems to be scratches is probably further deterioration. Viewed from inside tank, the surface seems normal. There as no place I could see that water was on the outside of the tank however.
 

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sailingdeacon

Member III
I am having a new tank built by FLORIDA MARINE TANKS INC. http://www.floridamarinetanks.com/ They have a location now in NC not too far away. The tank requires very precise measurements. They do not use the original .090 alum but instead use 1/8" thick so the tank will be heavier unfortunately, but much better quality. They also replace the pickup tube with non metallic.

I luckily had the drawings of the tank in the Ericson material. The cost was very, very reasonable: $300

The other two options I considered were:
1.. JB weld "It's water-proof; petroleum-, chemical-, and acid-resistent; resists shock, vibration, and extreme temperature fluctuations" JB Stick “It will even cure completely submerged in water or GASOLINE!” listed are “fuel tanks”
5. Marine tex Their email response was "For your particular application, the Marine-Tex Gray is recommended. Marine-Tex putty is resistant to both diesel fuel and gasoline, but over time, the fuels will begin to break down the epoxy. This occurs at a very slow rate, however. As a result, use extra epoxy and overfill the areas to be repaired. It will take the diesel fuel a very long time to get through the excess epoxy."
 

jkenan

Member III
Randy-

How did you clean and prep the tank so you could cut off the corner while it was still in your boat to eliminate the risk of explosion?

I think I'm facing the same task, unfortunately....

John
 

chaco

Member III
No wonder it Leaked !

Commercial Marine Alluminum Fuel Tanks are welded 3/16" plate.
1/8" is not adequate...IMHO :nerd:
 

sailingdeacon

Member III
The oem tanks were .090 which is even thinner than 1/8" being planned. The actual volume is only about 20 gallons, as opposed to the advertised 30 gallons... or at least 20 gallons or a little more is all that will go in my tank. (see the other thread on this topic) So I feel since the old one was strong enough for 20 years, 1/8" should be more than adequate. The builder says the tank will weigh probably 15 lbs more. But thanks for the comment. http://www.ericsonyachts.org/infoexchange/images/smilies/smile.gif
:)
 

Randy Rutledge

Sustaining Member
My tank was empty for several months and the fuel that had been in it was so old it probably would not have been a problem after a few weeks of being dry and open. If you don’t have a few months to dry the tank and evacuate it you can drop chunks of dry ice and water in the tank and that will fill the tank with CO2 and make it safe. I used a bone saw like you would use to cut up a ham or the like. The saw produced no sparks and did a reasonable job of cutting the sump off. About four inched was required to get it out of the hatch on the E29 port side locker.

The discoloration in the keeper part of the tank clened off with a brush.
 

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