View Poll Results: Which material is best for replacement fuel tanks? (Material cost in parentheses)
Poly ($1500) 13 23.64%
Black Steel ($2500) 8 14.55%
Aluminum ($4500) 16 29.09%
Stainless Steel ($5500) 4 7.27%
Other 14 25.45%
Voters: 55. You may not vote on this poll

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Old 12-17-2015, 11:39 PM   #21
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Highest quality alloy blend, thick material, properly welded, correctly installed - aluminum fuel tanks... For diesel or gasoline.

I recommend using Soltron additive to keep in-tank water a non issue for both fuel types.

Those are my # 1 choices for tank and additive! - Art
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Old 12-18-2015, 01:49 AM   #22
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TDunn,
Can you actually get monel these days? All kinds of things were made of monel back in the 50's including prop shafts and fasteners. Any idea how expensive it would be?
Very, I suspect.
How about titanium? Was used in space craft, now they make bicycles of it. Watches too, noticeably lighter compared with steel equivalents.
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Old 12-18-2015, 02:21 AM   #23
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Originally Posted by Art View Post
Highest quality alloy blend, thick material, properly welded, correctly installed - aluminum fuel tanks... For diesel or gasoline.

I recommend using Soltron additive to keep in-tank water a non issue for both fuel types.

Those are my # 1 choices for tank and additive! - Art
Thanks, Art. Good info on the tank quality but I'd rather avoid this becoming an additive debate.
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Old 12-18-2015, 02:32 AM   #24
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Another tank option would be a bladder inside a wooden box. At the other end of the scale from titanium, monel or whatever. Maybe a good option for an auxiliary tank.
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Old 12-18-2015, 03:34 AM   #25
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I voted "other", which = Fiberglass.
Can easily be build in any size/shape you wish, will wipe down clean clean, and last you a life time. No fuss, no muss, fit, monitor, and more-or-less forget.
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Old 12-18-2015, 03:40 AM   #26
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I went against the grain and voted for stainless, as this is what I used when replacing my tanks recently.


I'm surprised at the big price difference suggested, as the quotes I got were only slightly more than black steel. This was for stainless tanks almost double the thickness as the original stainless tanks.
My original tanks started to leak after over 30 years. The corrosion was external on the bottom where moisture collected under the tank. Internally they were like new. The replacement tanks were raised on mounts to allow air to circulate underneath, and gave slope down to a water drain point. I expect these will be good for a lifetime.


Just wondering why all the negative opinion on stainless.
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Old 12-18-2015, 05:32 AM   #27
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Quote:
Originally Posted by AusCan View Post
I went against the grain and voted for stainless, as this is what I used when replacing my tanks recently.


I'm surprised at the big price difference suggested, as the quotes I got were only slightly more than black steel. This was for stainless tanks almost double the thickness as the original stainless tanks.
My original tanks started to leak after over 30 years. The corrosion was external on the bottom where moisture collected under the tank. Internally they were like new. The replacement tanks were raised on mounts to allow air to circulate underneath, and gave slope down to a water drain point. I expect these will be good for a lifetime.
Just wondering why all the negative opinion on stainless.
The fear of hidden crevice corrosion I think, Auscan. Incidentally, my tanks are stainless, having been converted from water to fuel when the old iron tanks got the usual pox, by the PO. They are still fine some 15 years later. (Bugger, Jinx you never heard that, ok?). I have installed food grade plastics for water, and am now a fan of those. Fuel grade plastic would be my choice for any replacement fuel situation now, (See Headmistress Peggy's post), but I'm sure your stainless will be just fine, as mine are also elevated and air circulates. One thing they did right way back in 1975.
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Old 12-18-2015, 07:54 AM   #28
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I would vote for MONEL as a genuine fuel tank can easily be created.

With cost a factor the polly box for fuel would be OK for main tanks with a servicanble day tank to gravity feed the engine would be a second.

All the nonsense about fuel polishing and crap growing in the fuel need not exist if a genuine fuel tank design is used.

Hint , a fuel tank is not just a box filled with fuel.
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Old 12-18-2015, 08:01 AM   #29
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I don't think poly tanks can be easily made above a certain smallish size. I might be wrong there.
"Marine Fuel and Water Tanks

No matter what the size, shape or design, we can custom fabricate to the exact specifications required for a variety of boats and watercraft."

From the site Peggy put up a link to.
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Old 12-18-2015, 08:11 AM   #30
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Monel, a copper nickel alloy is alive and well. Sure it can be used for marine fuel tanks. But at around 6 times or more the fabricated cost per pound than steel, why do it? Especially with perfectly viable alternatives available.

Monel is great for Hxers, many of us have these cupro nickel units.
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Old 12-18-2015, 10:16 AM   #31
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The large (40-50 gallon) plastic/poly tanks I've seen online don't seem to have good inspection/cleaning ports.

These guys suggest their product can be used in plastic tanks...do you think these would reduce structural strength or have issues with tanks swelling when full? Seabuilt - Access Plate Systems
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Old 12-18-2015, 10:19 AM   #32
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This is off topic but was wondering at what tank capacity a baffle becomes desirable or needed?
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Old 12-18-2015, 11:04 AM   #33
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I don't think a poly tank would be cheaper than a black steel tank unless you can use a small off the shelf rectangle. A custom shaped poly tank (175 gallons in our case) would probably cost more than stainless steel. When it comes time to replace the tanks on Walkabout I will probably use steel. The existing ones are 38 years old and do not leak. I guarantee the new ones will be made with much more care than the Taiwanese put into these. 38 years from now I will be 94 years old. Don't think I will care at that point.
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Old 12-18-2015, 11:15 AM   #34
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I guarantee the new ones will be made with much more care than the Taiwanese put into these. 38 years from now I will be 94 years old. Don't think I will care at that point.
How do you possibly guarantee that when you have no idea how much care they put in and when the existing ones have lasted 38 years?
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Old 12-18-2015, 11:40 AM   #35
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How do you possibly guarantee that when you have no idea how much care they put in and when the existing ones have lasted 38 years?
Having crawled through, under, over, around this boat sanding, painting, repairing, replacing, adjusting, redesigning, rebuilding almost every system I am very intimately acquainted with the Taiwanese forethought and quality control of TTs of that era.
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Old 12-18-2015, 11:47 AM   #36
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The large (40-50 gallon) plastic/poly tanks I've seen online don't seem to have good inspection/cleaning ports.

Beckson Beckson Marine Inc.- Marine Hardware makes a full line of top quality retrofit inspection port kits. You'll find them under "deck plates."

Btw....when you visit their site, be sure to check out the "Rescue Friends" page.
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Old 12-18-2015, 12:28 PM   #37
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If I were to replace tanks I would opt for steel. Epoxy painted on the outside, installed with some air space around them so they could dry, and I would put a slight angle on the installation so any water would settle into one corner. I would have a inspection port put above that low spot so I could get any water out if necessary.
I would also make them smaller...I don't need or want 360 gallons of fuel aboard.
If I could get a poly tank in the 75-100 gallon range I might choose poly.
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Old 12-18-2015, 12:35 PM   #38
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Depends.....ask for a specific app and use...then I can be more specific.
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Old 12-18-2015, 01:46 PM   #39
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Just wondering why all the negative opinion on stainless.

As it was explained to me, welding changes the properties of stainless at the weld. In essence it becomes "not so stainless anymore." So unless the welding is done exactly right, the risk of failure at the seams from corrosion increases and the risk gets greater the less correct the welding technique becomes.

Different grades of stainless have different degrees of resistance to corrosion. For example, stainless prop shafts are usually made with one of two grades of stainless, AQ-19 and AQ-22. As it was just explained to me by the yard our boat is currently in, both grades are identical in terms of strength. But AQ-22 is more resistant to corrosion than AQ-19. (It is also considerably more expensive.)

For boats that sit a lot AQ-22 is usually recommended because the shaft at the bearings and seals will be deprived of oxygen for long periods of time and so will be more susceptible to the formation of crevice corrosion. For boats that get more frequent use AQ-19 is the most typically used grade.

This is why it's important with boats with stainless shafts to "excercise" the shafts periodically, either by running the boat or turning the shafts over to exchange the water in the bearings and around the seals and thus expose the steel to oxygen. If crevice corrosion attacks a shaft the ultimate risk is the failure of the shaft, usually suddenly and at an inopportune time, if there is even such a thing as a shaft failure at an opportune time.

So the grade of stainless a fuel tank is made from will play a role in how resistant the tank will be to corrosion at the welds as well as the welding technique itself. We have the work order and charges for the manufacture of the stainless tanks that were put our boat in 1997. The cost of the tanks was $10,000. According to what we were told the grade of steel used is pretty resistant to corrosion. However, these properties are changed at the weld line. So how well the tanks in our boat will hold up over time remains to be seen.

In tracking down a very complex problem with our PNW cabin cruiser one of the shafts has been found to have slight crevice corrosion at a wear point. While the shop said the shaft can be cleaned up and that they have seen shafts with the small degree of crevice corrosion ours has continue on for many years trouble-free we have elected to replace the shaft.

A fuel tank can set up the exact condition you don't want with stainless--- the metal is deprived of oxygen for long periods of time. If there is any opportunity for corrosion to get a toehold along the weld lines, the tank is on its way to eventual failure.

We have designed our fuel management process to minimize this risk. What our process' contribution is to the longevity of our tanks is anyone's guess.

The water tanks in our boat are also stainless, but the turnover in a water tank is generally much higher than with a fuel tank. So the steel in the tank is getting "oxygenated" much more frequently. If our water tanks are original to the boat--- they may not be--- they are almost 43 years old now. So far there are no leaking problems that we are aware of.
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Old 12-18-2015, 02:05 PM   #40
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"These guys suggest their product can be used in plastic tanks...do you think these would reduce structural strength or have issues with tanks swelling when full? Seabuilt - Access Plate Systems"

The size change (the tank grows after being filled with fuel) is simply part of a proper tank install.

Yes the boat gets the tank filled , then foamed or bolted in place.MFG dont like it because it adds labor to the out the door cost. The tank plate would then be added.

A bunch of plastic tanks would probably be great for a seasonal cruiser.

All but a small day tank could be drained , till the season begins.

Beckson sez,

A note about fuel tank mounting.
We do NOT recommend your using our deck plates for access directly into a fuel tank.
Through the deck above the tank? OK. But into the tank itself? No.
The diesel fuel would "eat up" the molded o-ring over time and would allow fuel to leak - a totally unacceptable situation. You are better off using an aluminum or stainless steel plate and a diesel-compatible gasket material, attaching this plate onto the tank with through-bolt fasteners.
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