Fuel tank leak

Umm, I've fixed a few fuel tank problems including alloy ones. If your insurance does not cover the damage you have 2 cheap options, firstly haul or dry out out if the boat is leaking too badly, or if the weld crack is below the waterline. Then either fit a plastic fuel tank inside the old one, or epoxy the crack or hole. Alloy welding is expensive, but it is in reality the best method of repairing a hole in particular.
Never use stainless for a fuel tank as it will eventually corrode. Plastic or alloy. Water tanks can be made of stainless.

If the hole or holes in the tank were caused by electrolysis, make sure you rethink where the various anodes are located and what material you are using. Danglies work best if you have to keep moving from salt to fresh water. Magnesium anodes in Fresh water, Aluminium in brackish and Zinc in salt water, (Might have the first 2 the wrong way around, so DYOR).
I have had to fix electrolysis holes in an alloy diesel tank that was inside a plastic, (Polyester resin), boat because the tank was earthed but the feed wire to the bilge pump was made of Copper. Alas the very bottom of the tank was in salt water, even though it was sealed in place with foam due to a void of some sort.
Net result was 3 tiny holes that I used some thicked up West system epoxy to fill after the local alloy welder made a real fork up of an attempt to weld the holes.
 
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If you change the design as porto suggested , could the insurance say is is not as per design and code if there was another claim.
 
22 pages of comments and supposition since November 21 st - lets not redesign the whole fuel system or redesign tanks - Bouba has not yet found the leak -it could just be a leaky hose!!! and based on progress to date it could be March before we are put out of our misery!!
 
Freebee said:
22 pages of comments and supposition since November 21 st - lets not redesign the whole fuel system or redesign tanks - Bouba has not yet found the leak -it could just be a leaky hose!!! and based on progress to date it could be March before we are put out of our misery!!
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All the hoses are visible and Boubas checked them .Eliminated .
If you could be arsed reading the 22 pages .

For you and PeteM convenience from post #175 …..as I can be arsed .D15E8C07-2C12-4425-BE5B-EB9828460195.jpeg
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Look at the lower pics lower tank edge …….so closely fitted to a flexing hull .No separate bearers to mount the tank to insulate the tank from flexing .
It will be a busted weld at the back .
Foolish to copy this again by running to Beny with a open cheque book .
 
Any thoughts on this apparent angle on the tank .
Clue for the non tech numpties one word = Stress .
Second word = concentration.

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Sharp angles and tanks a no no imho .
 
Once the tank leak is sorted, it might be worth considering foaming the tank in on either side. Very odd to see a tank with a strange rear edge as indicated with the blue line in the picture above.
 
TNLI said:
Once the tank leak is sorted, it might be worth considering foaming the tank in on either side. Very odd to see a tank with a strange rear edge as indicated with the blue line in the picture above.
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From your experience incredibly looking at the pics I’ve just posted from #175 ……and Beny …long shot but convince me they have NOT actually built in the tank to the space .Ie just two alloy pieces ( even though not marine grade ) and suitably baffled .

I mean what’s that grey material above the tank …..some sort of diesel proof sticky back plastic on the bulkhead( s) ??
Why is there no gap ?

Hope I am wrong ….this time .
 
Portofino said:
From your experience incredibly looking at the pics I’ve just posted from #175 ……and Beny …long shot but convince me they have NOT actually built in the tank to the space .Ie just two alloy pieces ( even though not marine grade ) and suitably baffled .

I mean what’s that grey material above the tank …..some sort of diesel proof sticky back plastic on the bulkhead( s) ??
Why is there no gap ?

Hope I am wrong ….this time .
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The grey stuff looks like heat/sound insulation to me and it looks like it (the insulation) is cut/shaped around the tank,rather than the tank being shaped round the insulation,or using the insulation as part of the tank itself.

Ie the tank continues under that insulation.
 
Is the item marked with the blue line some sort of insulation with a gap between the insulation and the top of the tank? Or perhaps I am reading the photo incorrectly?

Edit - the above beat me to it
 
Portofino said:
Any thoughts on this apparent angle on the tank .
Clue for the non tech numpties one word = Stress .
Second word = concentration.

View attachment 128286
Sharp angles and tanks a no no imho .
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I think you are misunderstanding the picture the grey stuff is attached to the deck above the tank and the tank top is some 50mm or so below this layer such that you cannot actually see the rear or sides of the tank.
 
Freebee said:
I think you are misunderstanding the picture the grey stuff is attached to the deck above the tank and the tank top is some 50mm or so below this layer such that you cannot actually see the rear or sides of the tank.
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Maybe .
Just putting it out there .
Why have that corner bit highlighted in blue ? I mean all the services are visible on top of the tank .
Why didn’t Bouba peel the silver stuff back to look down the gap , if there is one with a endoscope searching .
Folks have mentioned “ self tapper “ ( not me ) from behind a bulkhead….touching initially = electrolytic corrosion with time . Wouldn’t you want to investigate that ?
After all underneath access looks impossible looking at the pics .
 
Portofino said:
Maybe .
Just putting it out there .
Why have that corner bit highlighted in blue ? I mean all the services are visible on top of the tank .
Why didn’t Bouba peel the silver stuff back to look down the gap , if there is one with a endoscope searching .
Folks have mentioned “ self tapper “ ( not me ) from behind a bulkhead….touching initially = electrolytic corrosion with time . Wouldn’t you want to investigate that ?
After all underneath access looks impossible looking at the pics .
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Look at the picture with blue highlighting on the left a fuel shut off cock with a handle that clearly passes under the grey sound deadening showing that its above the tank.....the strange angle highlighted blue is irrelevant just how its been shaped or.......not..to stick under the deck not on the bulkhead you cant see the bulkhead in this picture its further away underneath.
 
Portofino said:
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Move it to a yard as I mentioned in the St Trop bay ….indoors over winter it with them .There are loads of yards .Loadsa hangers inland all over the place in the river delta …..it’s a boaty paradise with all the on shore back up you could ever wish for .If you want your bar stools upholstering in elephant foreskin some one around St Trop will do it …….oh hang on that’s already been done 50 y ago :)
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Wasn't that Whale foreskin and wasn't it Aristotle Onassis's Christina O . ??
 
I had a leak on my inspection hatches at top of tank when I filled tanks to the max. It turned out the rubber seals had split.
just a thought
 
So many pages and so many contributors , so what’s one more ?
Here’s what I would do , given the OPs practical restrictions and reluctance to dismantle everything that went into the fit out on top of the tank installation .
That sender unit will unbolt .
Unbolt it, dip a pipe in and pump out the diesel
Then follow up with a wet vac , maybe a rag on a stick, just get it dry if diesel
Bung an endoscope in there and map the tank internally , surfaces , edges , pressure distortions , welded outlets and how far down from the top face they might be .
Replace the sender unit
Then fill it with 20l of pigmented ( dyed) water
And wait
Nothing ? No dyed trickle into the bilge ?
Add 40l
And wait
Etc
Finally , go for it , fill it with pigmented water up to the deck vent . This will pressurise any dodgy weld or weeping joint , ‘flush out’ the root cause .
And if and when it leaks , well, it’s only water but by working progressively you really narrow down the likelihood of the source . Then ha, the tank has to come out of course ?
Well, in a book of clever offerings , that’s mine given where and how the boat lies right now, stuck and unuseable. Perhaps we can call this Solution 257 Mk2 of all of ‘em
Good luck B , it’s a boat, it’s fixable methodically
 
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