Marine Fuel Tanks - PLastic Vs Aluminium - The Pros and Cons Debate

Marine Fuel Tanks - Plastic Vs Aluminum

This isn't a thought that crosses every boaters mind, and unless you hold on to your boat for a long period of time, are rebuilding a boat, or got a boat with a bad tank, you probably won't ever read this article.  For those that do indeed find themselves in that smaller crowd, I hope to shed some light on this situation.  

There are 4 main materials that are used for marine fuels tanks; polyethylene, aluminum, fiberglass, and stainless steel, of which the latter two are not as common so I am directing this article to polyethylene marine fuel tanks and aluminum marine fuel tanks.   In addition, this article is intended for standard gasoline permanent mounted boat fuel tanks and not for diesel fuel. 

Since I am not an expert in metal or types of plastic, I am basing this article more on the known pros and cons of marine plastic tanks and marine aluminum tanks. Again, I am no expert on this, and much of this information comes from talking to many "experts" in the industry, as well as some research.  From my research, the following are my beliefs on the subject.  If anyone has any "cited" information to contradict my opinions, please chime in via the comments below this article. When I say plastic I am using the term loosely, as most tanks are made with some sort of cross-linked high density Polyethylene resin, or better known as HDPE.

Pros and cons of Aluminum and Plastic Marine Fuel Tanks. 

Plastic Poly Marine Fuel Tank:


1) A major advantage, and one that persuades me right from the get-go is that tanks made from this material aren’t susceptible to corrosion. I believe the tanks are made from HDPE (High Density Polyethylene). 

2) Plastic tanks, if properly made will outlast aluminum marine tanks.  

3) Plastic marine fuel tanks cost less than aluminum marine tanks.  

4) According to many experts, plastic tanks are “incredibly durable” and much more reliable than aluminum tanks for gasoline. Diesel fuel may be another story.  

5) Being a non metallic composite, plastic fuel tanks won't introduce galvanic action to other components on your boat. 

6) Newer polyethylene marine fuel tanks are not affected by ethanol. 

7) Polyethylene fuel tanks have stronger seams than aluminum.  I'm not say that plastic is stronger than aluminum, but for the tensile strength of each when compared to it's own counterpart, the aluminum seam would be weaker.  


1) To the best of my knowledge, most plastic tanks don't have baffles inside the tank to limit the swashing of fuel and undue stress on the tank walls.  

2) Plastic tanks release vapors and after a period of time your boat begins to smell of fuel.  Personally, I often smell a light odor when the boat is being stored for long periods, so when I do smell fuel on a boat I suspect it's coming from another source.  All boats smell of fuel regardless of the tank, so even though I have this listed under cons, I don't believe it is a deciding factor con.  

3) Limited selection due to most plastic tanks being roto spun in a mold, which makes custom plastic tanks expensive.  There are a few companies with a wide selection for the popular boats, but if you have a not so popular boat and need a plastic tank, well it may be a tough choice. 

Aluminum Marine Fuel Tank:


1) A correctly mounted aluminum marine fuel tank of high quality material, and  under ideal conditions should outlast the boat.  Some say they last 25-30 years, but I think they may go even longer as I've seen them past that mark and still in good shape.  I've also seen some in the 15 year range that looked to be 50 years old due to crevice corrosion as noted in the con below. 

2) Aluminum marine fuel tanks often have baffles in them to stabilize the fuel from swashing around excessively. 

3) Aluminum tanks are custom made, so getting one to match your boats design is a snap. A custom marine aluminum fuel tank can take advantage of extra space and allow for more fuel capacity.

4) Aluminum fuel tanks are stronger and resist punctures better than plastic.  Aluminum tends to dent and withstands more punishment. On a rebuttal side, I really don't see how a properly secured tank would be at risk, but during install this could be of concern.   


1) One of the biggest issues in aluminum marine fuel tanks are from builders foaming in the tanks.  Aluminum tanks do not like moisture over prolonged periods, and the foam against the tank enables major corrosion to occur.  The constant jarring of the boat eventually creates a seem between the tank and foam, which allows any moisture, whether from deck water running in or from simple condensation to do its damage.  A properly mounted aluminum will have good airflow around all surface areas, thus allowing it to dry.  Studies show that aluminum marine tanks are structurally sound for 10 years in most cases, and beyond that they begin to weaken and should be replaced.  

2) Buying an aluminum marine fuel tank of quality is easier said then done.  I'm sure you've seen stainless steel on a 40 year old boat that still looks new with no upkeep, yet the stainless on many of today's boats will rust out in a year or less.  This is simply due to the quality of the alloys.  Aluminum comes in different mixtures, and a lower grade alloy will not give you the 30 plus years.   The only real difference I see in the aluminum marine tanks on the market today are the thickness being offered.  The main protection in aluminum is the natural oxide on the surface of the aluminum.  A simple scratch removes this coating an opens the door to corrosion. 

3) The new ethanol fuel, as we all know by now attracts water.  As mentioned earlier, constant water in contact with aluminum will corrode the alloy, and is doing so with aluminum tanks.  Despite what you may have heard regarding aluminum marine fuel tanks having a protective coating inside is not true.  The protective coating is the actual oxide itself, and this gets destroyed as soon as the massive amount of heat takes hold from the welding of the seems.

4) Constant pressure and jarring of the boat puts a lot of stress on the aluminum welded seams, which are more apt to fractures.  I've never had a plastic seam on a decent product fracture unless it was dried out from sun damage, which won't be the case in the below deck fuel tanks .  On the flip side, my push pull platform has fractured at 2 of the 4 deck braces around the welds.

5) Due to Ethanol's action of attracting water, aluminum marine fuel tanks can and most often do create galvanic reactions throughout your boat. Zinc can be placed on the tank for exterior protection, but this does no good for the interior, thus leading to problems extending beyond just your tank, as well as corrosion attacking the welded seams from the inside out. 

6) Aluminum does not take well to alloys that are not of the same.  A simple loose bolt, screw, nut or any other metal object that were to fall on the tank and continue contact would eventually corrode that area.  Loose washers or other items seem to always find their way to the tank area.  In fact, as you may know we are doing a 225 Aquasport Osprey boat rebuild, and upon pulling the deck off we found several washers and screws that had been laying on the tank for many years, as evident by the fossil imprints they left behind. I have decided to go with Moeller, as they have a great reputation and also had the design that I needed.  Check the link above and follow the build.      

Conclusion of Aluminum Vs Plastic Marine Fuel Tanks:

Basing the conclusion on the winner between the pros and cons above really isn't fair, as there are many factors in determining the clear cut winner, such as the install being done correctly, airflow in the hull design, dry docked or wet slip, boat usage, maintenance, and many more.

I have a 55 gallon aluminum marine tank in my 1993 21' Hewes Light Tackle flats boat and after inspection it still looks new!  I have no idea what the inside looks like other than a very narrow look through the sending hole, which looked absolutely fine.  My tank is not foamed in so that gives it a fighting chance.  I know Hewes used all the best material available, as nothing on that boat has ever rusted that came originally on it.  The tank is not sitting on a wood bottom, and the support rails are angled to allow full drainage.  The entire tank has plenty of breathing room, and there are open air pathways that keep the air moving.  I have seen no foreign metal in contact with the tank, have put a meter on it and observed no current flow, so I am comfortable in saying that this tank should last the life of the boat.  

The example above is a good case scenario, however, with the introduction of Ethanol, there's no telling how long my aluminum tank will hold up.  I have always been a fan of aluminum, as it's stronger, and as far as metal goes, I feel it is the best alloy for marine use hands down.  But, since the introduction of ethanol, my favoritism is beginning to shift to plastic for marine fuel tanks. Plastic seems to be the winner by way technicality, as ethanol may be aluminum's Kryptonite.

 Allen Applegarth of      


+1 #1 Riley
I couldn't agree with this article more. Well said FIA. I have had to many issues with metal tanks and I'm done. Nice looking tank you put in your rebuild there guys. Did you have that custom made or is it off the shelf? Sorry to post over here but I didn't see anything on the rebuild page to post.
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It was an off the shelf tank, as a custom plastic tank would cost about 10k. Our tank was only 1/2 inch smaller end to end, but the capacity was the same somehow. Thanks for the comment.

+4 #2 Pete
Plastic for me. You nailed it FIA. I did go with metal however b/c I couldn't find the correct size plastic tank for my boat. Each has good point, but I think plastic takes the lead just as you have pointed out.
+3 #3 Poonman
I do a lot of rough water fishing and just feel more comfortable with metal having the baffles inside. I am able to get to my tank fairly easy so it's not that big of deal other than the cost if the metal goes bad. Either or I think is fine.
+4 #4 Hal Thomasson
The galvanized tanks in my 72 pacemaker have the lead peeling off on the inside of the tanks and after 40 years they need replacing. I'm leaning towards plastic, but the baffle issue has me holding back. Origional tanks are round so i"m going rectangle for more volume. Moeller has several plastic tanks in the 112 to 115 gallon range. still can't resolve the baffle issue. If anyone has these tanks installed in their boats please let me know if the baffle issue is a legitimate concern. Thanks
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Hi Hal,
I certainly see your concern, especially having multiple tanks. My new tank is roughly the same size as you are looking at, but my tanks sits low in the boat and I padded all sides out to 1/2 inch from the tank. Being that the center of gravity is so low, and the tank is surrounded by structure and padding, I don't foresee any issues with the boat being controlled by fuel movement.

Having 600 pounds or less sitting so low on a 6000 plus pound boat should not cause any noticeable movement in the boat overall. Being that the tank is narrow, side to side roll is my last concern due to very little distance to build momentum. The longer travel from end to end may produce more effects, but I doubt it will show any noticeable difference in bow to stern movement.

They do make a foam that you put into the tank aftermarket for this purpose, but I've never used it so I know nothing about it.

Also, the tank we removed was a Moeller, and nearly 18 years old and it was not secured as well as what we did for the new one, and yet it was still sitting in the original lock down position with no signs of wear from movement of the actual tank.

I would look at the placement of the tanks in relation to the center of gravity, the enclosures in which the tanks will rest, and possibly the aftermarket foam.

Please keep us updated on your decision and findings. Best of luck.

0 #5 Lenny
Great tanks. I installed one about 10 years ago and not a single problem. Someone commented about smelling fumes, no fumes in my boat unless i spill.
+1 #6 Rolando
1997 hewesLt20 I need a gas tank do you the size and how much is it thanks waiting for your reply rolando


Hello Rolando,
We do not sell fuel tanks, but if you want to contact Moeller I'm sure they will get you what you need.
+5 #7 Peter Eikenberry
I am considered by some to be an "expert" on fuel tanks and your article nails it very well. You presented all the pros and cons. I might note that both plastic and aluminum tanks have to meet USCG requirements for fire resistance and the plastic tanks do it just as well as metal tanks. Also the new plastic tanks that meet US EPA standards do not permeate vapor anywhere as much as ones made before 2012. So smell should no longer be an issue. Baffling is an issue on large tanks and if you are going to much more than 100 gallons you should have baffles to reduce sloshing. That means metal.


Hi Peter...great to see an expert chime in and give the article a thumbs up. Good note on USCG fire rating. Thanks for the comment. Happy boating / fishing.
Thanks for posting this info.I am looking to retank my 96 mako and feel better advised in doing so.Plastic seems to be the best solution for a 55 gallon tank based on your info.As you trust Moeller I will give them a look. Thanks.

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Thanks for dropping by Albert. You won't be disappointed in Moeller tanks. Let me know how it goes. Be sure to follow the install procedures. You can see mine by clicking the link in the article for the 225 Project Aquasport. Best of luck to you.
+1 #9 miguel Valdivia
This was just the type of reading I was looking for. Retanking my 1990 arriva 2450. Had a 60gal aluminum tank that was shot, was able to find a similar shape and just moeller tank but had to drop down to 52gal. I dont think ill miss the 8gals,only doi g lakes and pulled out the 454carb for a 350efi. Found a moeller tank with two vertical round tube shaped cut outs in the middle of the tank to act as baffles.


Glad the article helped. Thanks for leaving a comment, and happy boating/fishing! FIA
+1 #10 JG
Indeed thank you all for the useful comments. I was confused between plastic and aluminium for my Rybovich rybo runner 30feet 1984, well it is about time it leaks, so I guess for a tank of 180 gal aluminium should be better especially that Moeller does not have the shape I need and customized one will cost a lot. Ps correct me if I am wrong.

Thanks for the comment JG. You are correct. It will be a lot cheaper to have a fuel tank made from metal in this size. Happy Boating.
+1 #11 zchkhaidze
On my plastic fuel tank manufacturer print
producing year, month and even date. Will it means my plastic tank has a certain shelf live date

All tanks will eventually wear out, so in a since, yes that would be a shelf life. Old tanks are built like they are today with the new material, so if you are doubting your tank, the wise choice is to get a new one and it'll outlast your boat.
+1 #12 Mohammad ALKhabbaz
Good article I am in the process of changing my 80 gal tank and I am going for the aluminum :D , it's good I didn't go with the fiberglass tanks as I read they react with ethanol.


Can't go wrong with aluminum tanks as long as you install them correctly and don't foam to the tank. Best of luck and thanks for the comment.
+2 #13 mark tappert
how much air flow do you need under a aluminum tank

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It's doesn't matter how much, just keep a gap so air can flow around the tank, and also for expansion. I would do as much as possible, but no less than 1/2 inch. The other aspect is to ensure the tank is above the bilge water level. I put a bilge blower in my last boat that forced air around the tank. After trips I would run the blower for a few hours on a hot day.
+1 #14 Ryan
Great article! I am in the process of a new deck on my 86 21' Privateer
I am looking at plastic after reading. Can anyone tell me the best size to use for a four stroke motor for near shore fishin? It had a aluminum
40 gallon I want to up it but not increase weight so much.


Thanks for the visit and comment. There really isn't enough details to give you an answer, and there are many variables that will dictate what tank you need. You need to figure out what your GPH is for the motor and boat you have before anything. Factor in how often you'll be stopping at various spots, as frequent stops will eat up extra fuel when trying to plane off. Getting on plane drops my GPH down from 2.8 to .08 for about 10 seconds, so doing a lot of these will eat your fuel quickly. I like to have more tank capacity for my offshore boat, but my 20 foot Hewes flats boat has a 55 gallon tank and I can run all day with a 150HP 2 stroke. Fuel weights about 6.1 lbs per gallon.
+1 #15 David Kraus
Great write up! I can't tell how old it is but it has me looking at plastic tank options to lower the overall weight of my boat. It's a performance oriented 87' IMP Eleganza 25.5'. Tank is a 100 gallon Aluminium tank which is in great shape as the boat still has 100hrs or less on it the tank is in very good shape but looking good at plastic tanks to hold the likes of race gas and or e-85 for racing purposes only. Plus I don't need 100 gallons as I don't go to far more like 60-80 gallons is all I need.

Glad you liked the write up David. It's about a year old. Best of luck with your new set up.
+1 #16 Nancy Gold
How often should a plastic gas tank be replaced? The one in my Whaler is 12 years old. One side of it is uncovered and therefore exposed to the sun.

Hello Nancy. That is a great question, but also a hard one to answer without inspecting the tank or knowing the brand. (Talking permanent tanks) In the case of Moeller, with a properly installed tank, they will last the life of the boat. This also depends on its use, but one could get over 30 plus years on a tank. I'm not sure what size tank you have, or why it's exposed to sun, but UV exposure will certainly shorten the life. The sun will make the plastic brittle over time, and though it may seem flexible and sound, it could split easily. This is not something you want to risk, so if it were me, I'd replace the tank and find a way to keep in out of the sun. Some sun damage signs to look for are fine lines of darker color running through the plastic, white powdery surface when scraping, rough surface, and major color change. The old style yellow tanks will start to sparkle after they have turned darker in color, while red portable tanks turn white. Hope this helps.

Best, FIA
+1 #17 stephen
Aluminium contains magnesium which is highly inflammable and has a shelf life so the correct grade is important there are 53 common grades the more folds you designinto your tank less seams less potential leaks


Thanks for the comment Stephen. That's a great tip for the less folds equals less potential leaks. Yes, Magnesium is "highly flammable," correct you are.
+1 #18 megan
This is awesome information about fuel tanks! Thanks for explaining that there are 4 different materials that can be used for fuel tanks. So, having read the all of the pros of plastic ones, it seems to me that that might be the best option! I mean, if plastic marine fuel tanks cost less than aluminum marine tanks AND can outlast seems like an easy choice to me!
Megan |


Thanks for the good comments, and glad I could help. I certainly think today's plastic tanks are the way to go, and Moeller makes a great product.
+1 #19 michael
Great article. The starboard fuel tank on my 2013 Catamaran became riddled with pin-holes in less than a year. We found bits of brass in the tank from the threads of fittings, we found metal and debris under the tank abrading the metal and trapping moisture; insufficient rubber gasket for a 90 gallon tank; insufficient air circulation, no clean out port, etc..
I thought I had done something wrong, which is normal for a new boat owner, but it turns out the tank was built and installed to fail. Live and learn....and thanks for clarifying all I learned the hard way. BTW,I did replace the starboard tank with a factory tank, but will keep my eye on it and make sure to allow access to air an keep it dry. (Do need a clean out.) Thanks for the good work.
+1 #20 Marty D
Great info!! My 2005 2320 parker has 140 gall tank. It is foamed in all around the tank. I took the pie cover off to check the tank only to find the tank wet from washing the deck. The o-ring must of been leaking. I open both round pie hatch and put a fan to dry the tank and foam. I did this every day for two weeks. You you think that help dry out the foam? I took a pice of the foam out and squeeze it and water came out. I'm hoping using the fan on hot sept days the foam will dry. I called Parker boats and told them about this. They said they use a foam that doesn't or can hold water. That's not true. The tank is 10 years old. I have grandkids on this boat. I'm worried


Thanks for the comment. The so called "closed cell" foam is good while it is fresh, but from what I have seen, all foam eventually drys up and starts holding water, hence the issue with aluminum tanks corroding. I doubt a fan would dry the foam, and I suspect it would take many months of dry weather and applied heat/air circulation to begin to dry out the foam. Most of the moisture comes from the bilge area, as tanks sit above the open hull beneath to allow open bilge water flow. If it were mine, I would remove the foam and tank for inspection. The foam is a form of support, so I can only assume the tank will not function on its own with no foam. They do make tanks that can support their own outward pressure without need for foam. My Hewes flats boat had an aluminum tank, but no foam, and was in great shape after 20 years. Best of luck and better safe than sorry, so at least get it pressure tested above rated pressure to see if any weakness is present. The Ethanol fuel also corrodes the tank from the inside on the welds where the protective coating was baked off from welding.