Cleaning Out the Fuel Tank

[mbianka]

Three years ago I drained the 30 gallon fuel tank on my 1986 30 foot sailboat after converting to electric propulsion. Recently I started on converting the unused fuel tank to a fresh water rinse down tank. I cut an 8 inch access hole on the top and looked inside. I was surprised at what I found. You can see what the tank looked like here:
http://biankablog.blogspot.com/2011/04/in-tank-part-one-scene-of-grime.html
Even though I used a biocide religiously and changed my fuel filters every season or 50 hours (whichever came first) I did not quite expect to see this much coating on the bottom of the tank. I don't think a simple fuel polishing would have removed it either. I never really had a problem with clogged filters in the diesel days but, I could see how if this stuff gets stirred up in a heavy sea it could ruin your day when the filters clog and the engine stops. Thought others here might be interested in what I found. It was an eye opener.

[Tiki 38']

What do you think that stuff is? It is certainly different from the black hideous stuff that I hosed out of my tank recently.

[DeepFrz]

Yep, that stuff will not only clog the filters but the fuel line/pickup tube too. Its probably tar that precipitated out of the diesel fuel. If you put a little chlorine bleach on it and it stays black it is precipitate. If it turns whitish it is biological goop.

[rebel heart]

Fuel polishing is the ultimate in snake oil. If you have a clean fuel tank, you don't need to polish it. And polishing won't clean a fuel tank.

Open it up, drain it, wipe it clean with some paper towels, seal it back up. Free to do and not really that much work.

[DeepFrz]

Open it up, drain it, wipe it clean with some paper towels, seal it back up. Free to do and not really that much work.

And, IMHO, add a little "snake oil" in the form of a fuel polishing system.

[rebel heart]

Originally Posted by DeepFrz

And, IMHO, add a little "snake oil" in the form of a fuel polishing system.

Fair enough; I just don't see the need. If my filters are picking up junk I need to clean the tank. If they're not, the tank is clean. There just isn't any place for polishing in that equation and seems like a needless process.

[DeepFrz]

If my filters are picking up junk I need to clean the tank. If they're not, the tank is clean.

rebel heart, I have to disagree. Have you ever seen a pristine fuel filter and a clogged fuel line? I have and I don't ever want to see another one.

I agree that if the tank is cleaned regularly then a fuel polishing system may not be needed, but I would have one...if I had a boat <grin>

[mbianka]

Originally Posted by DeepFrz

Yep, that stuff will not only clog the filters but the fuel line/pickup tube too. Its probably tar that precipitated out of the diesel fuel. If you put a little chlorine bleach on it and it stays black it is precipitate. If it turns whitish it is biological goop.

Deep Frz:

I think you are right it probably is tar. I have not tried chorine on it but, with Simple Green it stays black. It felt like a thick resin when cleaning it too.

[mbianka]

Originally Posted by rebel heart

Fuel polishing is the ultimate in snake oil. If you have a clean fuel tank, you don't need to polish it. And polishing won't clean a fuel tank.
Open it up, drain it, wipe it clean with some paper towels, seal it back up. Free to do and not really that much work.

Certainly makes the case for installing a BIG inspection port on a boats fuel tank.

[rebel heart]

Originally Posted by mbianka

Certainly makes the case for installing a BIG inspection port on a boats fuel tank.

Getting your arm in there is a pain in the ass for sure with all the baffles and what not. I try to remember "you don't need to eat out of it". Just need to get the big clumps out and do as best a job as you can.

But for sure inspection ports that let you access the majority, especially the lowermost sections are critical.

[Tellie]

The benefit of fuel polishing depends on a few things. First not all boat fuel tanks are the same. Some just don't have access plates nor is it always feasable to install them depending on their location or ease of access. A good fuel polisher will agitate the fuel in the tank breaking loose quite a bit of crap and filtering it out. More than even a rough sea will create. Fuel is expensive, especially in larger boats that carry hundreds of gallons. Polishing that fuel before it is put back into the tank after manual cleaning is a very good idea. There are fuel tanks with access plates that only allow acess to one side of the baffle/s so hand cleaning the entire tank is impossible. Fuel pick up tubes will be of different heights off the bottom of the tank causing one tank to clog quicker than another. Polishing should be more of a maintenace routine instead of a cure for a neglected tank. Sometimes you just unknowingly fuel up with really bad diesel and a quick polish will save you a lot of headaches. A little Biocide goes a long way as does keeping your tanks topped off to prevent condensation.

[mbianka]

Where to place the inspection port was a concern of mine because of a possible baffle issue. So I put an inspection camera through the fuel sender to see if their was one and where it might be located:
THE BIANKA LOG BLOG: TOOLS OF A SAILOR: INSPECTION CAMERA
Happily, there was none so I was able to have pretty good access to most areas on the tank with just my arm. Took less than twenty minutes to do a first pass with paper towels in the 30 gallon tank.

[SailFastTri]

Mike I noted in your blog that the tank is aluminum. If you're going to use it for water you should figure out a way to line it or use a bladder. Aluminum will react in water and form aluminum oxide crystals that can clog pump filters, especially if you use chlorinated water.

[GordMay]

Originally Posted by Tellie

The benefit of fuel polishing depends on a few things. First not all boat fuel tanks are the same. Some just don't have access plates nor is it always feasible to install them depending on their location or ease of access. A good fuel polisher will agitate [sic: scour] the fuel in the tank breaking loose quite a bit of crap and filtering it out. More than even a rough sea will create. Fuel is expensive, especially in larger boats that carry hundreds of gallons. Polishing that fuel before it is put back into the tank after manual cleaning is a very good idea. There are fuel tanks with access plates that only allow access to one side of the baffle/s so hand cleaning the entire tank is impossible. Fuel pick up tubes will be of different heights off the bottom of the tank causing one tank to clog quicker than another. Polishing should be more of a maintenance routine instead of a cure for a neglected tank. Sometimes you just unknowingly fuel up with really bad diesel and a quick polish will save you a lot of headaches. A little Biocide goes a long way as does keeping your tanks topped off to prevent condensation.

INDEED.

[mbianka]

Originally Posted by SailFastTri

Mike I noted in your blog that the tank is aluminum. If you're going to use it for water you should figure out a way to line it or use a bladder. Aluminum will react in water and form aluminum oxide crystals that can clog pump filters, especially if you use chlorinated water.

Sailfast tri:

I already have two other potable tanks made of aluminum which have not been an issue. So this tank would not be that much of a burden and it also has a bigger inspection port to clean any oxides that may form. Ultimately, it will be mostly gathering rainwater to use for an occassional washdown of the deck and cockpit at anchor when things start to get to grimy on board. The use of a bladder tank is "Plan B" if the conversion does not work out as planned.