Diesel Tank Cleaning?

[Delancey]

Well, it wasn't easy, but I got the tank out of the boat. Now what to do with it?

I had heard some well meaning advice to drain the tank while it was in the boat, which is in the water, and add either detergent and water or gasoline, then rock the boat back and forth, drain again and repeat until it ran clear.

For me it was worth it to pull the tank just to clean up 28 years of grime and be able to paint that area of the engine bay and for that reason alone I am happy I did it.

Now that I have it out, I've made a couple calls around and as usual have found a couple different people who say a couple different things about how they would do it.

My money so far is on the radiator guy whose "been doing this for 40 years" but who also wouldn't be super specific about what he would do over the phone, which I can appreciate somewhat. He wanted to see the tank first.

The tank itself is welded .090 aluminum with baffles and a 40 gallon capacity. The fuel has been completely drained out and the layer of 28 year old sludge on the bottom has mostly dried up.

The radiator guy starts at $50 and goes up from their depending on what "it takes to get the tank 90-100% clean". This includes some sort of soaking, with what he wouldn't say. He also wouldn't say how long it would take but that it could be a couple days.

The other guy said that for $50 he would have "one of the guys in the yard power wash it with a wand" while I waited. He also remarked that he couldn't say how clean it would be when he was done but that he "maybe could try using some detergent" after I prompted him. Not a big confidence booster.

I don't really care about how much it costs, I just want to know the best way to clean it. Any advice would be appreciated!

[barnakiel]

Maybe (your cost/benefit analysis here) you will have the tank modified so that a well sized inspection hatch is fitted. Then cleaning it becomes a no-brainer - hot water, brush and detergent and you are done.

The added value is that you will be able to visually inspect the inside and tell how much life is left.

Cheers,
b.

[Delancey]

I am not necessarily adverse to putting more holes in an otherwise perfectly good tank. The general concept as I understand it would be to drill and tap around the inspection hole so that you could insert aluminum screws from inside the tank, then nut and washer on a plate with some type of gasket in-between.

At one point in the boat's history the PO had someone replaced the original electric sending gauge with a mechanical one which leaked there ever after. The PO appears to have overfilled the tank on an annual basis as the tank's plywood dunnage was completely pickled with fuel and there were fuel stains everywhere.

Not enough to discourage me from this option as I have much better access than the guy who installed the gauge before me. Certainly a sure fire way to get the tank clean. Before I go this route though I'd like to know if there is a less destructive approach?

[bobconnie]

Put the acess port in the tank ! in 5 yrs or so ya could have the same problem all over again !! with the fuel avaiable today, and the possibilty of water intrusion make the problems you have now a good possibleity for the future !! if you do it right once ya have it made for the future!! Ive had to do this myself a couple of times, and Im sure others have also! it's not really a hard job, nor is it an expensive job if you can't do it yourself. believe me it's not as hard as it sounds and the conveince of being able to clean the tank when and where you wish is worth the time and effort needed! just our 2 cents

[DeepFrz]

+1 on what Bob said.

[Cheechako]

how thick is the tank? many of those alum tanks are only 090 thick. Not too great for providing a flat surface for mounting a lid. Take it to a fab shop and they can get it done properly which may include welding a reinforcment on. you will likely need to use ss screws for strength... very easy to break off an alum #8 or #10 screw. shouldndt be an issue on top of the tank. Whether mechanical fuel gauge or elect sender the leak problem could have been there. Same mounting...
BTW: the new owner of a previous boat Ihad removed the alum tanks and had 3/16 bottoms welded over the 090 bottom which had pinholes in a couple of places. Worked out well. Might not be too expensive and make that old tank last another 20 years.

[Nemo55]

+1 and +2 on what Barnakiel and Bob Connie said....put the access panel in now,,,make it so it covers 3/4 of the area of the top side,,panel flange the edges and gasket and screw it....job done for lifetime.

[DeepFrz]

Before you spend any more money on the tank, post a couple of pictures of the bottom and sides.

[csmithers]

I put in an access/inspection plate. It took longer to put in the access plate than it did to clean up the actual tank (and it didn't take that long).

Seabuilt - Access Plate Systems

[rebel heart]

There is nothing you can do to clean the tank that will be half as good as opening it up and wiping it with paper towels. Whatever you do make sure there's an inspection port (or two) placed on top of it. Any decent metal worker can do that easy. You can buy gasket material (permatex) for a few bucks or spend more and get some diesel resistant ones made. Personally I like the fluid style that you just replace whenever you open the tanks back up. The "better" gasket materials tend to get crushed into position and seep.

[Reo Baird]

+1 on inspection port.

Cut out the rough opening your self, inspect the tank walls inside and out to ensure the tank is otherwise solid, if it is, have an inspection plate fabricated (the tank will have to be reinforced in this area... easy for someone with a welder... and then some studs installed).

To clean my tanks I simply remove the fuel and then vacuum the sludge and crud out with a shop vac through the inspection port.

[The Way]

Here's what I did to my monel 20-gallon cylindrical tank with baffles. There was no access hatch for cleanout, and I wanted to avoid cutting one if possible.

I emptied the tank and removed it. In the cockpit, on some old towels, I poured in 2 cups TSP and 7 gallons boiling water. Sloshed that around every few minutes for an hour, then let it sit overnight. Then disposed of the TSP properly. Washed the tank out with a hose, trying to spray walls and baffles. Then rinsed with 1/2 gallon alcohol and let dry. It's shiny inside now!

Take the opportunity to replace hoses and grounding wire also. And most important, the O-ring on the filler cap.

Good luck!
The Way

[mbianka]

Originally Posted by barnakiel

Maybe (your cost/benefit analysis here) you will have the tank modified so that a well sized inspection hatch is fitted. Then cleaning it becomes a no-brainer - hot water, brush and detergent and you are done.

The added value is that you will be able to visually inspect the inside and tell how much life is left.
b.

I'd also recommend putting in an inspection port. I cut one into the former on board diesel fuel tank that I'm converting to a fresh water wash down tank:
THE BIANKA LOG BLOG: IN THE TANK: Part One, Scene of the grime!
After a full strength Simple Green and paper towel wipe down. I followed it with a handheld steamer that made the inside shine:
THE BIANKA LOG BLOG: IN THE TANK: Part 2, Steaming Ahead!
You've done the hard work (removing the tank) now make it easy for yourself to inspect and clean the tank in the future.

[Jetexas]

I cleaned mine by boiling pots of water, pouring the boiling water into the tank, then picking it up and shaking it around. I kept doing this until I stopped getting anything nasty when I poured the water back out.

My friends who do car tanks actually put a bunch of chain in the tank to break up the rust and gunk while they shake it around. As long as you leave chain coming out the filler tube you can just pull it back out.

[neilpride]

A year ago i move to the dock a 50 gallons alu tank from a Hunter 42, 1 baffle in the midle , no inspection plates and about 3 inches of **** in the bottom,
I cut 2 inspections holes in each side of the baffle, shoap , detergent , water , and lots of scrubing and flushing made the tank shine inside again, now come the part to cover the inspections plates , i buy a large aluminium plate in the rigging shop ,
I cut the plates 2 inches larger than the holes, drill and tap every one and half inch , i know sounds lots of screws but this keep the plate as flat as posible and avoid gaps between the gasket and the tank, and use a rubber gasket , be sure the rubber gasket is all the way from corner to corner with the size of the hole, tuffgel in screws , good quality screws, fill the tank with some diesel and put it upside down for the whole night , no leaks next morning so project done ,
btw remember that algaes and dirt stick to the suction pipe , fuel lines and filters, i replace both, fuel lines and filters to, and flush very well the suction pipe.
Cheers.