Rust on Fuel Tank - Opinions?

Went to see a 1985 Taiwanese Trawler today. These pictures show the top of her port side steel fuel tank. Clearly lots of surface rust. The area around the tanks is quite dry. So I have two questions:
1. Is this amount of external rust typical on a 1985 boat and does it mean internal problems are likely?
2. Is the round thingy on top of the tank an inspection port?
Any advice and input is appreciated.

David

Greetings,
Mr. DR. From my very limited experience, that seems like a LOT of rust, even for a Taiwanese boat. Indicative of long term deck leaks IMO. No real way to tell the internal condition without inspection. I suspect that do-hickey one sees through the deck is a fuel gage sending unit. Where is the boat located? Salt water?

She did spend two winters in the Bahamas 10 years ago. Otherwise she is a fresh water boat. I agree that is a fuel gauge gizmo - just wondering if you remove it can a surveyor get in there with a camera on a wand of some sort, and can he look at what's accumulated in the bottom of the tank?

Greetings,
Mr. DR. Usually surveyors are not willing/allowed to remove stuff for inspections unless permitted by seller.

You could probably pop the filler hose off - just visible to the right in the 2nd picture. But I don't have any guidance on whether a surveyor could discover anything. Is the tank in service? How full is it?

Yes the tank is in service. The boat just came back from a 1 week cruise around Lake Ontario.

That much Rust on an '85 TT iron tank? How lucky are you feeling these days?
Time to buy some lottery tickets or a trip to Vegas.

My tanks had enough rust on them they scared me...not easy...

They looked like the bottom of most bridges in nowheresville going to the island offshore.

Yet when I cut them out...they were as sound as the day they went in..I think.

A tiny fraction of an inch of meter produces copious amounts of rust.

All you can do is inspect from the inside, pressure test, beat with a hammer...etc...etc..

Well if the tank was made of 1/4 inch thick plate probably not much to worry about-yet. But I expect the tank is made of much thinner material than that. You can test the thickness of the plate but I think you should just figure that the tank will need replacement. Also you need to find out where the (likely) deck leak is that caused all that rust. Then you also need to look and see what other damage there might be from a leak.Price out the potential repairs and go from there.

Two options IMO if the boat is otherwise everything you've dreamed for in a boat.

#1 Make an extremely generous offer contingent upon seller replacing all fuel tanks. (All other things being equal I'd personally not have a problem offering more than full asking price)

#2 Make a fair offer contingent upon you hiring a mobile fuel polisher to clean and inspect the tanks at your expense.

#1 is always my go to play regardless of item considered for purchase.

I sent those pictures to a highly regarded local surveyor to see what he thinks.

David Rive said:

I sent those pictures to a highly regarded local surveyor to see what he thinks.

Click to expand...

Pictures can be invaluable for a guess at best...those pics for a guess...guarantee it will only be a wild guess....

My tanks had way more rust but still had 90+ percent of the original metal around the filler necks. But I didn't know that till I cut them up.

My surveyor friend says the best thing is to try and see the underside of the tanks, which he says is usually pretty hard to do.

Anyway, I am going to go ahead and make an offer and see what happens. She looks like a great boat in every other way, as far as I can see. The survey (which will include a diesel mechanic inspection) will hopefully tell me more. Hey - I may be a new owner by the end of the week! We will see.

Thanks for all the input folks. This is a great Forum!

I'd run, like gump.

9 of 10 probability that the source of the water which caused this is the deck fill fitting is no longer properly bedded to the deck. 1 in 10 it is coming from somewhere else (like a hawse hole), running a ways along an edge, and dripping onto the tank top.
Make sure the cap is tight, then spray the fill fitting with a freshwater garden hose then check the tank top for fresh leakage.

The tanks will be useful in negotiation. If you survey and buy, treat the tops of the tanks for rust and apply the specialist rust refinish. I fixed worse tank tops than that, though query for how long.
You need to understand, and if you buy,fix the water entry. I`d be more afraid of that (?decks), and what that will cost. Another negotiation issue. Tread carefully.

Mine is a 1989 Taiwanese although some rust not even a small % of what this looks like from the picture

my surveyor uses a scope to look down the fill line as he said this only gets a broken visual of a very small portion of the top of the tank

The rust looks dry and , if it comes off with a finger wipe its not bad for 30 year old iron in a not very ventilated spot.

Deck leaks , house leaks ,window leaks might flood enough water to have thinned the tank top.

Then chunks will come off on your finger.

IF there are no signs of the usual TT internal shower , you might simply use POR 15 or similar to treat the tank top and worry in another 30 years, IF you can keep it dry.

One option if you have leaky rusted tanks that are hard to replace is to use something like an ATL fuel cell.Either the Fluorocell and Supercell models.
I'm interested to hear from anyone who has used one.
I've done a few tank replacements and it gets serious very quickly.
Might save ripping an interior to bits.
My main tank is about 3100 gallons and it's looking suspect rusty inside and out,it also is underneath 3 cabins,2 bathrooms and a hallway,so removal is a destructive process.
At least it has manholes so I can climb inside.Can't wait.
Anyone used one ?

This is the stuff...
Rust Preventive Coating
coat it right over tight clean rust and forget it forever

That tank rust looks minor next to mine. I peeled three layers/sheets off before I got to solid material. The solid material had holes in it. Mine are 1989. There is another good thread on this subject.

If that much rust is on top and there is a deck leak,I'm sure that there will be MORE rust were that water pooled under the tank. Replaced my tanks as rust was at seams and inside the tank were the tank cleaner had broken rust free dearing the cleaning . The tanks will need replacement at sometime in the future.

stornoway7 said:

One option if you have leaky rusted tanks that are hard to replace is to use something like an ATL fuel cell.Either the Fluorocell and Supercell models.
I'm interested to hear from anyone who has used one.
I've done a few tank replacements and it gets serious very quickly.
Might save ripping an interior to bits.
My main tank is about 3100 gallons and it's looking suspect rusty inside and out,it also is underneath 3 cabins,2 bathrooms and a hallway,so removal is a destructive process.
At least it has manholes so I can climb inside.Can't wait.
Anyone used one ?

Click to expand...

I have used them helping a friend deliver a boat but never replacing they seemed very well made

BTW we need more pics of your boat she is a beut

I am familiar with ATL and FuelSafe cells in auto racing applications. They are made to very high standards to meet the specifications of various sanctioning bodies worldwide and I would assume their marine cells would be no different. However, the quality comes at a high price. IIRC an 18 gal fuel cell for a low horsepower formula car was over $1800 (included the fillplate) in 2006. The mode of fatigue failure was either age combined with embrittlement of the polymer due to ethanol (older cells) or most commonly chafe points at the corners of the cell. Vibration producing relative motion between the "bladder" and its containment structures will eventually cause leaks if this is not compensated for (I lined the structure bottom with thin sheet neoprene as this is where it failed most often). I would think that in an application using an existing fuel tank as the containment structure one must make sure the interior of the structure is smooth/non-abrasive...not likely if the interior of a metal tank is severely corroded...and the area where the baffles were removed is ground smooth. I would guess that the prep work and fuel cell cost may exceed the cost of other more conventional replacement options. This, of course, is speculation based upon experience in non-marine applications. YMMV

Great input! Thanks everybody.

Well, my offer on the 1985 Ocean Alexander 38' was accepted. Survey (including mechanic) and sea trial is Thursday. Wish me luck.

Good luck...I hope it all works out well for you!