But speaking from the experience that I have seen with 10 years in the marine industry, pulling up many decks and replacing many fuel tanks. I would say No. In most cases the fuel tank compartment is sealed tight or even glassed in under the deck. Foam does not absorb water, leaving the water to sit around the tank and eventually rust or corrode it.
Though there are a few manufactures and cases where the foam did act as a sponge and just suck up and retain all of the water. However, for most cases, the water would just sit in between the foam and the tank. The foam would act almost as a big bucket or bathtub retaining the water against the tank, actually speeding up the time in which it takes the water to corrode holes in the fuel tank! This occurs even with the marine grade, two part, heavy duty, expensive foam! So, no, foaming around a tank does not add to a fuel tanks life span.
The idea of taking an aluminum fuel tank and putting it into a boat bare, to most people seems like a very bad idea. Leading them to think that coating the tank with an epoxy type coating will help to add to the fuel tanks longevity. We have a friend of ours that has been in the custom boat restoration and fiberglass business for over 40 years. He has seen his share of fuel tank replacements and deck removals in his time in the industry.
He says that there was a time when they were coating the tanks with epoxy. Sanding the aluminum and scratching it up, cleaning it with chemicals, and then sealing it with the epoxy. What they found was that over the years, the epoxy would do the same thing as the foam would. It would get blisters, cuts, scratches, or air pockets that would pop.
Giving an entrance point for moisture. Creating the same premature corrosion issues on aluminum fuel tanks. With this discovery, they stopped coating their replacement tanks. But, given the testimony from the custom boat restoration and fiberglass expert, I would say I believe his testimony and think that bare is the way to go.
Replacement tanks should be built to fit the location they are being put in. The best way to install a fuel tank and secure it is to have tabs welded onto the tank that can be secured to the stringers of the boat. You want to make sure that they are fastened on at least four point of the tank. Depending on the length of the tank, six points is even better. If you are not getting a custom built tank and purchasing a general size tank, it still needs to be secured.
If the tank tops were angled they may have shed water, giving users a clue as to the impending failure. Tanks should be installed in such a way as to enable easy, casual inspection, i. Deck fills, in teak decks are notorious for leaking water onto tank tops. The gap between this deck fill and its bedding is clear to see.
Inspect your deck fills and tank tops regularly. A final note on tank installations relates to serviceability and accessibility. Covering or sheathing a tank for cosmetic or acoustic purposes is a double edged sword, it may look more attractive, to some, or it may offer minimal of any noise reduction in accommodation spaces, however, it also means that leaks, corrosion, deteriorating hose and other issues may go unnoticed.
Many boat builders cover tanks with a fascia or acoustic insulation. Tanks should remain exposed, particularly metallic tanks. Spacer material should be bedded to tank bottoms, like that shown here. Doing so prevents water migrating between the tank and the spacer. Finally, horizontal metallic tank tops should be slanted or angled to shed water, and they should angle inboard to ensure that leaking water runs down the side of the tank that is visible such angling is required for compliance with ABYC standards.
Deck fuel fills are notorious for leaking water onto the tops of tanks why deck hardware leaks, and how to avoid it, is the subject of an upcoming Marine Systems Excellence article , where it often stands, ultimately causing rust or corrosion on steel and aluminum respectively.
It is imperative that cushion material, regardless of what form it may take, must be bedded to the tank. Inspect your tank installations. If your metallic tanks are covered with an aesthetic or acoustic barrier, consider removing it or improving access for inspection purposes. As a boat owner, few feelings are worse than knowing you could have avoided a costly failure by identifying a problem before it became critical. If you are considering buying a boat, give tank access and inspection careful scrutiny.
Tanks should be designed, built and installed to avoid failure, at least from the outside in, for the life of the vessel. Sign in. Log into your account. Password recovery. There will be situations where this method will have to be modified.
Aluminum tanks are not expensive, so if you need to make modifications to the original shape, be prepared to do so. Just remember that the objective is to avoid creating points that create crevices and trap water. Here are few other points to consider;.
First posted on May 23, at David Pascoe's site: www. Page design changed for this site. Visit yachtsurvey. Links to pages of each chapter contents at davidpascoe. Chapter 1 What is Pre-Purchase Survey? Boat Reviews. Power Boat Books. How to Install an Aluminum Fuel Tank. Crevice Corrosion Here's the answer that many of you asked for on how to install an aluminum fuel tank so that it doesn't corrode and leak again.
New Deck For replacing tanks foamed under the deck, between stringers, or tanks just sitting on a bare plywood deck, you need to build in a new deck. Mounting Deck The best method for mounting the deck is to fasten heavy, fir ledger strips to the side of the stringers. Points to Consider There will be situations where this method will have to be modified. Here are few other points to consider; Never allow water absorbent material such as wood to come in contact with the tank.
Do not use rubber strips: rubber contains carbon, which is cathodic to aluminum and will cause galvanic corrosion. It is best to use only stainless steel pipe fittings for the fuel supply. Do not mix a variety of metals. Do not use steel or galvanized. Make sure that whenever the tank is sitting on is a stable surface; always use the hull stringers and never the bottom of the hull. Make sure that straps or whatever securing devices you use don't cause crevice corrosion.
Tank should not be so deep in bilge that it's going to be in constant contact with bilge water. About Author: David H. Pascoe is a marine surveyor retired with 40 years' experience.
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