Fuel tank on 30 year old trawler

How much of a concern should an original steel fuel tank on a 30 year old boat be? Am looking at used trawlers for purchase. Should the possibility of replacing a rusted fuel tank be high on my worry list or is this unusual?
Based upon my readings, they can corrode from the inside and may look okay but then leak and replacement can be major headaches and $$$.
Is this true or just an unusual worst-case scenario?

Hydrophilic said:

Is this true or just an unusual worst-case scenario?

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Very true from what I've read here...

It's all about protecting them from water...inside and outside. But it's hard to know without getting a camera or set of eyes in the tank.

I bought my 1985 boat 3 years ago with no issue so far with fuel tanks. 4 stainless steel tanks 3/8" tick. Got them checked last year with no issue so far...

Francois said:

I bought my 1985 boat 3 years ago with no issue so far with fuel tanks. 4 stainless steel tanks 3/8" tick. Got them checked last year with no issue so far...

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With stainless I wouldn't worry much, (given a good original installation)...With mild steel, as used on many of the Imported trawlers from the 70's and 80's, I would..It's a very big expense, especially if it requires pulling the engines to replace..

I would say 30 years would be the average life of a tank. If designed and installed properly they could last much longer, but most have problems that develop over time.

I just replaced both of my 32 year old stainless tanks. They corroded from the bottom due to being mounted directly on to a flat surface without breathing space between tank & deck. One started to weep diesel slowly; the other started after I cleaned it.

If their is any chance of water getting under, or on top of your tank and sitting there for an extended period of time they will definitely corrode. Also if water sits inside a tank for an extended period it will corrode.

Have a look at the design (outlet height, water drain point, slope) to see how the tank is designed and this may give an indication of life expectancy.

FlyWright said:

It's all about protecting them from water...inside and outside. But it's hard to know without getting a camera or set of eyes in the tank.

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And that is very hard to do in most installations..

My 1985 has had one? tank replaced by a PO. Go figure. They had to pull the engine for sure, why not do both?

If you can look at the top of the tanks and are mostly rust free, and the filters do not have water in them, I would say your odds are pretty good that they will not leak in the near future.
But, no guarantees.

Stainless tanks are subject to pinhole corrosion and galvanic corrosion particularly where they sit in straps and are in contact with sea water.
Always get them checked in and out, and move the installation straps etc. Slight pitting etc can be solved with proprietary coatings and fillers

30 years is definitely getting up there for steel tanks, but there are certainly examples of them lasting longer. Any boat that old should have the tanks carefully checked and pressure tested. There are pros and cons to each tank material. A common problem with tanks is that the deck fill can be directly above the tank and if not rebedded at appropriate intervals can allow water to leak directly down on top of the tank. Steel tanks that have been subject to this are usually severely rusted on top.

Steel, aluminum, stainless or fiberglass tanks can all last almost indefinitely under perfect conditions. However, things happen or the installation is less than ideal. Any steel or aluminum tank that has significant water in it (from water in the fuel) or water regularly dripped or splashed on it will have a shortened life.

Ken

This is an area of concern to me. The 1988 Krogen 54 I am buying has 3 tanks (1200 gal total) that seem in great condition on the outside. They have a green epoxy coating that is in very good shape (as much as we can inpect!). Of course I don't know what the insides will be like. No water in the Raycors. I plan to drain down the tanks and then check the insides when I get the chance.

Richard

Britannia said:

This is an area of concern to me. The 1988 Krogen 54 I am buying has 3 tanks (1200 gal total) that seem in great condition on the outside. They have a green epoxy coating that is in very good shape (as much as we can inpect!). Of course I don't know what the insides will be like. No water in the Raycors. I plan to drain down the tanks and then check the insides when I get the chance.

Richard

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If you've got inspection plates, it's not too bad. I know a company in the area, Cruising Seas out of Fairfield, CA, who can install the plates and inspect the tanks. They did so for me while polishing the fuel and scrubbing the tanks following a failed deck fuel cap which allowed 4 gallons of water to enter the stbd tank.

They were great folks to work with.

The odds are that mild steel tanks will need to be replaced. On most trawlers it is both expensive and a pain.

Any trawler over 25 years old without the tanks having been replaced will be suspect and the price likely discounted. Of course there is likely an exception.

Francois said:

I bought my 1985 boat 3 years ago with no issue so far with fuel tanks. 4 stainless steel tanks 3/8" tick. Got them checked last year with no issue so far...

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Think you mean 3/32" (approximately 12 gauge). 3/8" thick fuel tanks would weigh as much as the fuel they hold. Ok not really, but you get the idea.

Ted

O C Diver said:

Think you mean 3/32" (approximately 12 gauge). 3/8" thick fuel tanks would weigh as much as the fuel they hold. Ok not really, but you get the idea.

Ted

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I was thinking that stainless steel must be cheap in the US. a ⅜" stainless tank would cost a fortune here in Oz.

My new SS tanks are 3/32". $550 each for custom built 100 litre tanks. The original ones were only half that thickness.

I replace two 158 gallon tanks several years ago and both engines had to be pulled, total cost was around $12,500. Not that big a deal considering it was a 1985 vessel.

kchace said:

Steel, aluminum, stainless or fiberglass tanks can all last almost indefinitely under perfect conditions. However, things happen or the installation is less than ideal. Any steel or aluminum tank that has significant water in it (from water in the fuel) or water regularly dripped or splashed on it will have a shortened life.

Ken

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My boat is not 30 years old nor a trawler. In 1967 manufacturers like Owens, Chris Craft and others built boats that where in no way efficient users of space so fuel tanks looked like tanks and not the fuel boxes tucked in a corner that is common among later vintage boats. A few years ago our mild steel tank was pulled, cleaned, inspected, painted and reinstalled. Lifts out of the hatch located directly above it, if the tank was empty I could easily have it sitting on the dock in less than an hour. Should be good to go for another 50 years.

We could gain a huge amount of storage in the laz if we switched to a fuel box. Since we are neither long cruisers nor live aboard's it would be a pity to change what works.

For me it is all about design, mild steel is a perfectly acceptable material if designed and installed properly. If not budget your replacement while writing your purchase offer is my advice, even if that replacement may be years down the road.

FlyWright said:

If you've got inspection plates, it's not too bad. I know a company in the area, Cruising Seas out of Fairfield, CA, who can install the plates and inspect the tanks. They did so for me while polishing the fuel and scrubbing the tanks following a failed deck fuel cap which allowed 4 gallons of water to enter the stbd tank.

They were great folks to work with.

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Thanks - yes the tanks have good sized inspection plates. So at least I have those in place.

Richard

The tanks in my 1981 IG rusted on top, due to deck leaks. The rust was treated on both, one needed the filler tube repaired, but touch wood, the tanks seem otherwise ok after 34 years.The degree of difficulty replacing depends on location, fortunately IG located my tanks NOT behind the engines. I dread replacement, but it could be worse.

Hydrophilic said:

How much of a concern should an original steel fuel tank on a 30 year old boat be? Am looking at used trawlers for purchase. Should the possibility of replacing a rusted fuel tank be high on my worry list or is this unusual?
Based upon my readings, they can corrode from the inside and may look okay but then leak and replacement can be major headaches and $$$.
Is this true or just an unusual worst-case scenario?

Click to expand...

As everyone else said. . . maybe good. . .maybe bad. But what's more important than the tank, is where it's located and can it be removed easily. Mine are under the aft beds and can be lifted right out by hand, when empty.

But some require extensive dismantling to be removed. If that is the case, then worry about those tanks. The cost of a new tank, maybe miniscule compared to the labor cost to remove it. Assume it's bad until proven otherwise. Be sure and have somebody knowledgeable give you an estimate to replace..