moellers wont corrode lol....some people complain about fuel smell but its a boat..

make sure if you go with a moeller you allow for 3% growth in all directions as the tanks are exposed to fuel they expand. I filled mine and let them sit for a few weeks then installed them.

 

26yrs in the marine fuel tank cleaning business and never saw a failed plastic/poly tank.

 

I went with aluminum after my plastic tanks split at the seams. Both starboard and port tanks had leaks

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Generally speaking, the anti-slosh baffles suck in plastic roto molded tanks. On a shallow and long tank as you describe, it becomes even more critical to keep fuel where it belongs. That's one reason why I prefer aluminum tanks over the poly tanks. Sure a poly tank will work and never corrode, but if you begin sucking air when you still have 1/4 tank of fuel left, you can thank the lack of good baffles for that.

 

As I read the post and saw the comment on the split tank I thought of leaking. And I don’t have the issue, thank god, but I do have fuel and oil spill coverage. I tend to be one who like to have insurance and the peace of mind. Not a tank reply, but maybe related.

 

If you can get to it for an inspection down the road, either would be satisfactory if installed per manufacturer's instructions. Good luck.

 

under 100 gal i would definitely go plastic. big joe showed a bad plastic tank, it can happen. i can show you 100's of aluminum

 

On a small tank, ie < 50 gallons, plastic all the way if there is a standard model that fits.

90 gallons is on the end where that's a pretty big plastic tank, I'd shoot for aluminum.

In between, a judgement call that may very much come down to availability, ie if there's a 65 gallon plastic tank that fits just right - I'd say plastic.

The nice thing about smaller plastic tanks you can buy from say Moeller, they are extremely cost effective and are sitting on a shelf waiting for you.

I do not think plastic tanks typically split, nor do I think aluminum tanks typically corrode, in practical terms. 20+ years is a long time to run a given fuel tank, they all typically last that long.

 

That appears to be a weld failure in the plastic tank pictures.

 

Had same thing happen twice!!

 

All of this feedback is very helpful and very much appreciated- thank you

 

On the subject of fuel tanks, does anyone know if an aluminum fuel tank for diesel can have a metal, fuel fill, standpipe located inside the engine box? I've read what I can find and have not found any guidance on it yet.

 

As long as the manifold and turbo are wet I can't think of any issues. But, I've never seen it before. IMO, it's nice to have it directly over the tank so you can stick it. Some sort of splash guard is nice also.

Hopefully the ABYC people/police will chime in on what the standard is

 

had a poly tank break on me too. Not fun.

Most important lesson is to put them where you can get to them somehow…. They will all need replacing.

 

had a poly tank break on me too. Not fun.

Most important lesson is to put them where you can get to them somehow…. They will all need replacing.

Ditto. Only 10 years old.

 

...but, but....it never happens?

 

Those broken welds are from a poly tank builder not a molded tank from Moeller though correct ? Not apples to apples
If you go with a tank from Moeller it’s not going to break , it’s molded . if you can fit one of their standard sizes it’s the best option.. It will last forever and it’s about 1/2 the cost of aluminum. Only thing I don’t get about the Moeller tanks is the mounting. They should put tabs on them

 

Quite true. Maybe it comes down to having baffles where you'd like them and custom locations for the fittings - if needed.

 

Yea that pic is a plastic welded tank. Moellers are roto molded from HDPE like an ocean kayak….very very strong material.

Also tanks need room to grow and for some reason they don't make it explicitly know that they need to swell when they are first filled. I could see how this could lead to failures creating hard points after install with 3% growth….or people who foam them in when they are not supposed to.

My tanks are 70 gallons and have two molded in baffles.

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I'm with Bill - are we talking the custom made plastic tanks or the off the shelf production tanks by Moeller/others?

I know someone personally who had a custom one split, but also am not aware of the production tanks ever splitting. They do read you the riot act in the instructions, but still not aware of one splitting.

 

All in the specs!! Rotomolded VS welded!! Not the same construction and even though both are tanks, they are not the same!

 

I also know of two welded plastic tanks splitting at welds. I would never use one. Rotomolded are pretty bulletproof. Surrounding them with full even support across the bottom is best. The 3% dimension around sides and top for possible expansion is where that counts. Aluminum is fine if you can keep it airy and dry around all sides. With plastic feet under the baffles and structure. Bonded with a liberal application of 5200. Aluminum should not be coated. These are recommendations straight from Luther’s welding in Bristol RI. I had an above deck tank they built in for modification last winter. They can take wet areas but don’t expect longer than 10 years. Foamed in can make it shorter. I know that from my Novi tank failure. 22’ outboard. I went rotomolded on that replacement. No room below deck for a dry vented space.

 

That's a good point on the mounting area and venting.

My skiff has a Moeller tank. There is no room under that deck for good venting, granted I did not foam it in or anything, it truly is not a great place to be mounting an aluminum tank. It's framed with a mix of PT and ceder and the tank sits just an inch or so under the deck panel that makes the span. I've got a vent in the front of the center console, another at the transom, to move fumes along/out, but generally it's just very wet in there always.

Granted it's only a 25 gallon, that one has gone 20 years so far. My main concern with it has been in recent times, I can't seem to turn the pickup fitting, is frozen somehow - has come up maintaining this or that: solution, resist those thoughts and do things a different way . But I bet if I really tried to unstick it that probably would be the death of the tank, no real need.

 

i think they sell fittings you can install too. Cut a hole and then have flanges with gaskets, or replace existing.