Older boat - fuel tank questions

Old 01-14-2019, 03:12 PM
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I think poster meant the layer of oxide that forms very quickly on aluminum. Very tough stuff, but it's no FlexSeal.
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Old 01-14-2019, 04:19 PM
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Originally Posted by lurker25 View Post
Granting this poster is probably long gone but....please elaborate on how aluminum is self sealing?? I would say most tanks that are over 20 years old are at a significant risk of failure but mounting can accelerate or prolong deterioration.
aluminum is self protecting through oxidation IF there is adequate ventilation around the tank. The oxidation process makes any water trapped against the tank very acidic, and the acid, not the water itself, corrodes the tank. If the water can dry through adequate ventilation, OR if the acid can be diluted by being in a lake or ocean, the aluminum will never corrode away. Aluminum boats, t tops etc will oxidize but never corrode away, but aluminum tanks corrode via crevice corrosion all the time.

Google “crevice corrosion” and you’ll have your answers on how some tanks last forever and some leak’s all whether small amounts of highly acidic water can be trapped against the tank for long periods. Installation makes the difference.
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Old 01-14-2019, 04:26 PM
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Originally Posted by Absolute View Post
We find aluminum tanks have an average life of 12 years and as they approach 20 years it become more certain of failing. Poly tanks while they do not fail the same way as aluminum tanks, they do have their pit falls mainly in the metal attachments.

It would amaze me if a surveyor would perform the necessary test to make a proper evaluation.
Open inspection hatches and look in there w flashlight or camera. Any rust on top o tank? Check the bilge. A dry bilge means a longer lasting tank. Is the bow at least a foot higher thaan stern while boat is on trailer? That is another positive. Good luck..

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Old 02-04-2019, 01:35 PM
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Both failed tanks I replaced were boats that sat in salt water in marinas. They both had similar designs, a hull shaped tank sitting in the bilge on hard neoprene cusions, screwed by tabs on the top. On the Monterey, after re-doing everything, I sealed the fuel tank compartment off from bilge water and it worked perfectly. The 2001 Monterey failed in 2015, the 2001 Chapparal failed in 2016.
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Old 02-04-2019, 03:45 PM
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My boat was built in 1988 . The aluminum fuel tank sits in foam and is fully encapsulated. The entire boat has been a project. One of the first things I did was pressure test the tank. It held 4 psi for 24 hours. I thought huh? The rest of the boat hasn’t been taken care of why is the tank good?
I then decided to check further and cut out a few areas so I could drill through the foam and do a smell test . All was good! My point is it all depends on the installation
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Old 02-04-2019, 03:54 PM
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Still have a 1998 Starcraft 22’ had to replace the tank years ago. Pin holes in it. 2-3 pound pressure test told all for me.
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