---

Hi, I am overhauling my 1986 outrage 18'
There is a 63 gallon aluminum fuel tank under the deck. The paint on the top aspect was in bad shape so I stripped it with stripper then mineral spirits. The tank itself appears to be in good shape with a few small areas of mild superficial corrosion. The access hatch at the bottom end was removed and the old fuel drained. The tank looks good on the inside, as far was we can tell.. The hatch was then replaced with a new gasket. I trimmed any foam that was coming up over the edge of the tank and then singed the foam with a heat gun. Now I am almost ready to refinish the top of the tank. (The sides and bottom are not accessible). Trying to decide what to do (if I paint it I want to use something I can buy in a spray can):

1) Leave it unpainted. This seems to be a common practice with aluminum.
2) Paint it with zinc chromide. Toxic and old-fashioned?
3) Use a product like Rustoleum self-etching primer? May not work well long-term without some other top coat?

In the past the boat has been kept in an arid state and used infrequently on fresh water. Now it will be kept in western Washington and be used frequently on salt water.
Any tips on prepping the surface?
Thanks

---

I don't know why Boston Whaler uses foam around their aluminum tanks as that is the surest way to guarantee corrosion will occur. Modern aluminum fuel tanks are built of a highly corrosion resistant alloy but the moisture trapped by the foam will eat through the toughest aluminum eventually. I don't have a built in fuel tank on my boat but I have had them on others and without a doubt the best thing you can do for your tank is insure an adequate flow of fresh air around it. How to accomplish that on a whaler is something I have no clue about. I doubt painting the exposed surface of the aluminum will provide any additional protection from corrosion.

---

I think I have been quite lucky regarding the foam. It seems to be in good shape although its obviously difficult to inspect the sides and bottom of the tank. I plan to reseal the deck and all screw holes with 4200. Anyone have any other tips on resecuring the deck?
Fresh air - I suppose I could pop the small round access ports while the boat is not in use.
Any other opinions on this matter (painting)? Surely others have done this task..

---

Scrape any loose paint and clean any oil/reside. Use a spray or brush on paint for aluminum. Nothing special.

As for re-attaching cover, check the holes and if oversized, fill with marine tex and re-tap.

3M's 4200 is an adhesive sealant and is not a suggested product. I would use a standard marine sealant (NOT SILICONE). There are some owners who demand a color match to the floor. Many vinyl siding companies offer sealants in the appropriate color.

I personally used white Boat Life brand. There is also 3M 101, Sikaflex etc.

It is recommended to pull the inspection covers to allow any moisture to vent when the boat is not in use.

---

Thanks for the tips!
Does Sikaflex 291 qualify as the proper kind?

Also is it a good idea to inject some into screw holes before refastening the deck. How about when fastening the console and the chairs back to the deck? Those attachments are a source of moisture penetration right?

---

Always use a good quality marine sealant, not silicone' on any fitting that screws into the fiberglass. The sealant will prevent water from penetrating the glass to the foam or plywood backing. It also will seal the screw or bolt and prevent crevice corosion which is common with stainless steel fasteners. I always use 5200 or 4200 because they have never failed me but like outboard brands, you will get as many different opinions as there members on this site.

---

I have a question.

I have always heard that the reason aluminum fuel tanks are always intentionally left unpainted in boats is due to electrical currents between saltwater and aluminum causing corrosion.

Is this correct, and if not, why do boat manufacturers leave them unpainted?

---

I found some links on the net that are very interesting about painting aluminum, both with marine fuel tanks and the boats themselves. It would appear that, as you have noticed when removing your fuel tank, and also I noticed when removing mine from the 1986 Outrage 18, Boston Whaler used some kind of extreme barrier between the foam and the tank that is VERY hard to remove from the outside of the tank. I think this is required due to the standards by which the boat was built. See this PDF:
http://www.google.com/url?sa=t&rct=j&...1363,d.b2k

Contrary to what others have posted regarding painting aluminum fuel tanks, it appears that there is a process that must be followed in order to paint aluminum. The aluminum must be chemically prepped and primed before painting or foaming in order for the paint or foam to stay on the tank and not actually cause more corrosion than leaving it unpainted. See this, and scroll down to the section entitled "The Trouble with Tanks".
[url]http://www.boatingmag.com/boats/protecting-aluminum-boats-salt-water-corrosion
[/url]

Also, this: [url]http://www.fishingunited.com/forum/viewtopic.php?f=22&t=440
[/url]

I am sure there are many more good references available regarding aluminum fuel tank painting, but these are a few I found. I have left my built in Boston Whaler fuel tanks unpainted upon boat restoration, and instead have tried to insure they meet ABYC standard externally between the tank and the foam, just as Boston Whaler originally did when my boats were made.

---

Many Coast Guard aluminum vessels are not painted. The alloy of aluminum used in those boats and hopefully in fuel tanks, will, when exposed to the elements, create a surface layer which protects the underlying aluminum from corrosion. It's similar to the gray surface layer on the aluminum yard furniture in your back yard only more durable because of the alloy composition.

---

So regarding technique (screwing down the deck), does one inject sealant into the hole and then drive the screw, or does one drive the screw and then seal over the top of it?

---

I inject into the hole and also put a dab on the screw thread. A rag dampened with acetone will clean it up nicely as long as you don't remove or thin down the sealant.