When to Replace Fuel Tank

[pspear43]

Give me information about the proper time to replace the fuel tank in a 1987 [REVENGE]

[Moderator's note: the author originally asked about a boat identified as a "Revenue."]

BACKSTORY: [I] have assumed [the tank to be at] end of life.

My mechanic says [I should] wait until [the fuel tank] leaks, as [the fuel tank] may last five years or more.

The boat has been used lightly, been dry in winter, and used in freshwater much of the time.

[The replacement of the fuel tank] is [a project] I will hire out and not do myself.

[jimh]

Give me information about the proper time to replace the fuel tank in a 1987 [boat].

In 2023, the condition of an aluminum fuel tank made in 1987 will depend entirely on how much water has been allowed to sit in the fuel tank cavity, and whether the water was fresh water or saltwater. Another factor is the type of gasoline fuel that has been in the fuel tank with regard to the ethanol content, and further if the fuel used was ethanol-gasoline blended fuel, if there has ever been a phase barrier between the gasoline and water that separated out from the gasoline. Another influence is the access to open air ventilation for the tank to help remove moisture by evaporation.

If gasoline fuel is leaking from an aluminum below deck fuel tank, there would be a noticeable odor of gasoline that would easily be detected.

There is no set timetable at which an aluminum welded fuel tank as used by Boston Whaler must be replaced.

A good method to test the integrity of any fuel tank is to perform a pressure test of the tank.

[Phil T]

Expect to pay $3,000 to $5,000 for a boat yard to replace the fuel tank.

If it ain't broke, why fix it?

[msteinkampf]

I think the advice given by Jim and Phil is reasonable, but I do have some additional suggestions and comments.

While it is certainly true that there is no "expiration date" for aluminum fuel tanks, problems do become more likely as the tank ages; the risk of fuel tank failure also depends on how the tank is installed and maintained.

The aluminum fuel tanks in my 1990 Montauk 17 are in excellent shape, with no significant corrosion, while the aluminum fuel tank in my new-to-me 1995 Aquasport Explorer 245 had already leaked and required repair by a previous owner. I found another leak when I removed and inspected the tank shortly after I purchased the boat. The tanks were made by reputable manufacturers and have seen their share of saltwater exposure.

The 1990 Montauk 17 fuel tanks are above-deck, are maintained either completely full or completely empty, and are drained, cleaned, and inspected at the end of every boating season. (Actually, I fill one tank and leave it in the boat, while the empty tank is stored in my basement.)

I have exclusively used fuel [blended at a gasoline-ethanol ratio of 9:1 ratio]. I always added a fuel [stabilizer additive] unless I expect to use up the full tank volume of fuel within a few days.

I don’t know much about how my Aquasport’s tank was maintained, but I can say with certainty that the installation method used by the factory contributed to the deterioration of this below-deck tank. (To see the details of my fuel tank repair and reinstallation, go here: https://classicaquasport.com/smf/index.php?topic=16118.0)

I’m not familiar with your model Boston Whaler, so I examined some photos of a 1987 Revenge 22 WT currently offered for sale online. Good news: the deck above the tank compartment appears to be screwed in, so you won’t have to cut the fiberglass if you ever need to replace the tank. There are also two inspection ports in the deck above the tank. These are required by federal law, and they are probably located above the tank's hose connections. I don’t know how your tank was installed, but my guess is that it is foamed in place. The attachment of the foam to the tank is supposed to be stronger than the foam itself so that if the foam ever shrinks, the interior of the foam will split while remaining tightly adherent to the tank, but in reality a small crevice may develop between the foam and the metal as the foam ages.

Aluminum fuel tank corrosion most commonly occurs via two mechanisms: (1) “crevice corrosion”, where moisture is trapped between the outside of the tank and the system (e.g., foam, rubber, metal straps) holding the tank in place; and (2) Corrosion occurring on the inside of the tank due to water collecting at the bottom of the tank under the fuel. My Aquasport tank had both types of corrosion. The tank was half-full with no fuel smell or other signs of leakage, but when I pulled the tank and pressure tested it, I found a pinhole at the aft end of the bottom of the tank. Lesson learned – the lack of fuel leakage does not rule out significant tank corrosion. The tank being stored half-full by the previous owner was an indication of how the internal corrosion had occurred, since that sort of storage seems to increase water accumulation in the tank.

Your mechanic is correct: your boat's fuel tank could last five (or twenty-five) years, or it could fail tomorrow. I am not aware of any legal requirements (or even consensus guidelines) regarding maintaining your tank. You could do nothing and wait for signs of leakage, or you could remove the deck cover, pull out the tank, inspect and pressure test it, coat it with coal tar epoxy or something similar, and reinstall it, preferably using some modification of the “Pascoe method” (https://www.yachtsurvey.com/fueltank.htm).

If it were my boat, I would take a middle course:

• Remove the inspection hatch covers over the tank, examine the fuel hoses and fittings, and look for signs of moisture.
• If you see water in there or there is obvious moisture on the top or sides of the tank, start saving your money for a new tank.
• At the end of each boating season, I would leave those hatches open to allow the fuel tank compartment to dry out.
• If the hoses and clamps are original to the boat, they probably need to be replaced.
• If you smell fuel and the hoses and fuel sender look OK, have the tank pulled, inspected, and repaired or replaced.

• If this has never been done, remove the fuel sender, inspect the interior of the tank, and insert a hose so that you can sample the fuel at the very bottom of the tank.
  If the tank is on a trailer, crank the trailer jack up so that the boat is in a bow-up position, allowing any water in the tank to collect towards the stern.
• If feasible, do this at the end of the season when the tank is almost empty, and siphon out all the fuel through the sender port before doing the inspection.
• Clean out any water and sediment you find, reinstall the fuel sender (and replace its gasket, it’s probably deteriorated), and refill the tank with fresh gas, either right then or the next time you use the boat. I’ve read that some boat storage facilities won’t store boats with empty tanks, so this may determine your choice.
• If I found a lot of water or sediment, I would repeat this at the end of every boating season, and I would change where I purchased my fuel. If I didn't find much water or sediment, I would repeat this every three to five years.
• Use a fuel preservative whenever you fill up the tank. Although you still run your boat while there is water and sediment in the bottom, you are more likely to clog up your fuel filters and even damage your engine if you have that junk in your tank and operate in rough water, stirring up the tank contents (and I speak from bitter personal experience). In my opinion, minimizing the amount of water in your tank will also prolong its service life.
• If you don’t want to do this yourself, your mechanic may be able to help you find a service that will test and “polish” your fuel for you, removing any water and sludge that has accumulated, and they should be able to do it without emptying the tank (although they will need to pull the fuel sender.)

• I wouldn’t bother to pressure test the tank unless it was removed for inspection or after repair. That test necessitates that all the hoses be removed or plugged and requires a knowledgeable service facility to do the test correctly. I don’t think it’s worth the hassle and expense in your situation.

I see a tank that fits your boat is currently available from Welding World in Miami, Florida, for $1,600 plus $800 shipping (see here: https://weldingworldinc.com/collections/oem-replacement-fuel-tanks/products/boston-whaler-22-revenge-77-gal-nominal-oem-replacement-fuel-tank)

You can consider that as a guide for replacement cost.

If you get [a replacement fuel tank] fabricated locally, I recommend you use the Welding World specifications, which are 0.190-inch 5032 aluminum, coal tar epoxy coating, and quality hardware. I would prefer to see the fuel sender installed closer to the aft end of the tank so you can service it via an inspection port. And know that any fabricator must be able to certify that the tank meets federal requirements for tank integrity.

Please let us know what you wind up doing the boat fuel tank.

[jimh]

On a c.1990 REVENGE 22 Walk-Through boat there are four pry-out deck access plates that allow access to the fuel tank area.

[msteinkampf]

Thanks for pointing that out. Perhaps the additional hatches allow access to the fuel sender. If so, the Welding World unit should work without modification.

M

[jimh]

Regarding the speculation about where the four pry-out deck access plates are located on the deck of a c.1990 REVENGE 22 Walk-Through, the locations are as follows, proceeding from forward to aft:

1. centerline larger opaque plate over the fuel fill inlet in the tank
2. center line smaller clear plate over the magnetically-linked tank level dial indicator with 270-degree arc of dial scale
3. larger centerline opaque plate of the fuel tank pick up fitting
4. starboard side smaller opaque plate over the ridge between the rigging tunnel and the fuel tank cavity where there is a brass grommet allowing for passing through rigging from the fuel tank cavity to the rigging tunnel

I hope this clarifies where the pry-out deck access plates are located on a c.1990 REVENGE 22 W-T boat.

[pspear43]

Thanks all for the comprehensive responses.