Fuel polishing--dirty diesel fuel tanks

Hello: Wondering if anyone on the forum has had the problem of a dirty diesel fuel tank. I have gotten quotes from around 4,000 to do a "polishing" but would not like to pay that much.

Is there someone here that has done that cleaning, and can tell me the procedure?

We are thinking about putting "sea foam" in the tank, has anyone here tried that?

Looking for a solution prior to fishing season.

To follow up, what the effect is that my boat stalls out due to air in fuel tanks and I have been advised that is due to blockage. Also, that eventually there will be a larger problem in that the dirty fuel will damage the engine.

The diesel fuel is a very dark color similar to varnish.

Greetings,
Mr. O. Welcome aboard. I think you're dealing with 2 different issues here. How old is the fuel? What fuel filter set up do you have before or on the engine(s)? A good filtering system should protect the engine from damage due to fuel contamination but you may have to change the filter element(s) many times. Buy a case.
Everyone has air in their tanks and that is NOT the reason for your stalling. It could be your fuel pump is sucking air from a leak between the tank and the pump or the fuel line is, in fact, blocked.
Personally I wouldn't worry about color. If the fuel burns, it's good IMO.

How many tanks? How many gallons of fuel?

I just had the fuel in one of my tanks 'polished' after seeing lots of crud in the filters. It took 2 guys about 3 hours to pump 200 gallons onto the dock and through their filters, then back on board. I was charged about $700 for this, which I thought was fair. Lots of crud was removed. There was limited scrubbing and vacuuming of my tank when empty since there is no side inspection port, lots of baffles in the fiberglass tank and just a 2 inch hole at the top for access. Still worth doing though, based on the look of their filters when they were done.

My Marine Diesel Maintenance instructor insists fuel polishing is "snake oil". Your filters are your polisher if they're maintained and operating properly.

Ken E. said:

I just had the fuel in one of my tanks 'polished' after seeing lots of crud in the filters. It took 2 guys about 3 hours to pump 200 gallons onto the dock and through their filters, then back on board. I was charged about $700 for this, which I thought was fair. Lots of crud was removed. There was limited scrubbing and vacuuming of my tank when empty since there is no side inspection port, lots of baffles in the fiberglass tank and just a 2 inch hole at the top for access. Still worth doing though, based on the look of their filters when they were done.

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The price is based on time generally, which depends on quantity of fuel and number of tanks. It also depends on what they do beyond polishing the fuel. How much cleaning of the tanks is done.

Also, some label it polishing when just running it through filters and polishing is more than that.

schrater is right. Polishing is the new snake oil.
Traditional diesel installations have two filters. A primary and a secondary. The primary is usually 30 microns and the secondary 10. You can buy a smaller micron rated filter in both places. Because most diesels engines pump much more fuel than they burn, most is returned to the tank to be filtered again and again.
With a fuel conditioner, you polish your fuel every time you run the engine. My current boat sat 6 years without any mothballing. I used a good conditioner at 3x the normal mix and went to a 2 micron primary after the 1st couple hours on the original 30 micron. It never plugged and I still run a 2 micron 6 years later. I couldn't inspect the tanks without removing the galley so a couple years later in a remodel, cut entry ports and went inside. Tanks were clean except for a little clean debris the pumps wouldn't pick up. 1942 steel tanks. I use a fuel conditioner/catalyst every fueling. It helps remove water in the primary where I can drain it, and gives me about 10% better mileage.

Ideally, you pump the old fuel out of the tank and filter it. While you are doing this, you cut holes in the tanks that will give you enough access to clean the crud out of the tank, then you put the filtered fuel back in. Not cleaning the tank means you are just wasting your money as a significant amount of crap will stay in the tank.

While the tank is empty and if you don't already have same, install a drain at the lowest part of the tank so you can drain out any water that settles. Water is the medium that biologicals will live in in your diesel so getting rid of that prevents more growth. If you use your fuel lots, the water will not have time to settle and it will just be consumed by the engine or if too much, removed by your filter system. Most boats sit around lots so there is plenty of time for water to settle.

10 and even 30 micron filters are very fine; the threshold of visibility is 75 microns. Surely filtering all particulates over 10 microns our of diesel fuel is sufficient for the engines in these boats? And at that, it doesn't matter whether you run your fuel through a 10 micron fuel filter on its way from the tank to the engine, or through a 10 micron "polishing" filter on its way out of the tank, through a $700-$4000 process and back into the tank.

That said, getting a bunch of particulate out of ones tanks seems wise as it sounds like fuel filters reach the point of clogging where engines starve at the most inopportune time.

Guessing for $700-$4000, you can buy a pretty sophisticated fuel filter system and plenty of spare filters, true?

Xsbank said:

Ideally, you pump the old fuel out of the tank and filter it. While you are doing this, you cut holes in the tanks that will give you enough access to clean the crud out of the tank, then you put the filtered fuel back in. Not cleaning the tank means you are just wasting your money as a significant amount of crap will stay in the tank.

While the tank is empty and if you don't already have same, install a drain at the lowest part of the tank so you can drain out any water that settles. Water is the medium that biologicals will live in in your diesel so getting rid of that prevents more growth. If you use your fuel lots, the water will not have time to settle and it will just be consumed by the engine or if too much, removed by your filter system. Most boats sit around lots so there is plenty of time for water to settle.

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If you saw the junk that was removed from my tank, I doubt you'd think I wasted my money. The fuel returned to my tank was filtered to 2 microns. And, if you'd like to put a drain hole in the bottom of your tank, have at it. Tell me how that works out, especially when your bilge water starts smelling alot like diesel.

One might argue that polishing on the boat regularly is snake oil, although I'd disagree with that. But that's not the OP's situation. He fuel is already in the tanks, he can't use filters to prevent problems as he already has problems. His is absolutely the situation in which a fuel polisher can help him significantly. Yes, if you're careful about everything going into your tank, filter it properly, you should never need this, but he inherited a mess.

Ken E. said:

If you saw the junk that was removed from my tank.

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Ken E.
I trust that. But removed junk from fuel may mean a lot more still in your tanks. Junk in your fuel was a direct consequence of dirty tanks, not the cause.
Time will tell. Anyway a pump out then 2 microns filtering was better than nothing.

BandB said:

I'd disagree with that.

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The very same here.

Snake oil....? That may depend upon what state you are starting in. I think perhaps if you are starting with clean fuel and clean tanks and then regularly run through a lot of high quality fuel, the onboard primary and secondary filtration will likely preclude the need to polish.
However, I think I can attest to the fact that if you inherit or acquire dirty fuel in a dirty tank and do not love changing dirty filters in a challenging seaway then polishing fuel through an external apparatus and thoroughly cleaning the tank(s) while the fuel is out is worth the spend. For me it was around 2K which included some boat surgery and access port installation. See before and after pics and decide if you would like to deal with the mess in the first two photos while underway through your onboard filters. Not fun for me that day. Last photo is worth what I paid for it. Tanks are right at thirty years old and look great with the junk out of them.

We inherited some real old fuel in one boat that we bought. It was unused for at least 3 years and did have that varnish type color that you referred to as well as many solids floating around in the tank. In most every case just pulling the solids out does not bring fuel of that condition back to an acceptable condition for combustion so we pumped it into 55 gallon drums. Passed that fuel through a 30 mic filter and used it in my home oil burner at a ratio of 1 to 4 with normal fuel oil.
We pumped to the bottom of each boat tank utilizing a length of soft copper ice maker line so we could reach all the low spots in the tanks. Then added a few gallons of fuel in each to the high sides of the tanks 'washing' remaining crud down with the same icemaker line as an outlet this time. Once again pulled from the lowest point in each tank and then added fresh fuel and was ready to use the boat from then on.
I used the same vane puppy pump the we use to change the lube oil to pull and pump the fuel oil.
No problems after that for the next 6 seasons until we eventually sold that boat.

Unless you can agitate all the fuel very well and get into each baffled area polishing is "snake oil".

At least in my opinion.



"And, if you'd like to put a drain hole in the bottom of your tank, have at it. Tell me how that works out, especially when your bilge water starts smelling alot like diesel."

Sorry, but that is a rather ignorant statement.

A proper stripping port located at the lowest spot on a fuel tank is a good thing. And not at all likely to leak.

Capt.Bill11 said:

Unless you can agitate all the fuel very well and get into each baffled area polishing is "snake oil".

At least in my opinion.



"And, if you'd like to put a drain hole in the bottom of your tank, have at it. Tell me how that works out, especially when your bilge water starts smelling alot like diesel."

Sorry, but that is a rather ignorant statement.

A proper stripping port located at the lowest spot on a fuel tank is a good thing. And not at all likely to leak.

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Well, that's good to know. Funny how fuel tanks, without exception, have their stand pipes for fuel withdrawal at the top rather than at the bottom. Might have something to do with leak prevention over the long term? And, sorry for my ignorant assessment.

Ken E. said:

If you saw the junk that was removed from my tank, I doubt you'd think I wasted my money. The fuel returned to my tank was filtered to 2 microns. And, if you'd like to put a drain hole in the bottom of your tank, have at it. Tell me how that works out, especially when your bilge water starts smelling a lot like diesel.

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1. If viable cost wise, a polishing/filtering process that substantially improves stored fuel quality is worthwhile, even if short of perfection.
2.A proper drain hole in the bottom of a tank is a good idea. IG36 tanks have a screw in plug at the bottom of the tanks. Brisboy recently replaced his with valves to facilitate drainage. Maybe Ken is saying that putting a drain hole in a piece of sheet metal not designed to accommodate a drain is likely to have problems, he could very well be right.

KenE, both the boats I've owned with diesel tanks took the fuel from the bottom of the tank. That is also where the crossover is located. The return for both my boats was at the top of the tank. If you have a sight gauge, your bottom part of the gauge is, SURPRISE, at the bottom of the tank. Take another look at Bill's tanks and see how the success of your filtering works out for you.

A ball valve in the very bottom of your fuel tank needn't leak unless you suck at plumbing.

Unless you have a powerful enough pump to stir up all that sort of crud in the bottom of your tanks and behind the baffles etc, the only advantage of pumping your fuel round and round is to keep your injection pump cool. If you have a circulating pump that keeps running while you are away from the boat, that circulates the fuel through some filters, that will only benefit you by keeping the water (that's in everybody's fuel) in suspension.

Diesel fuel has water in it from the refinery, plus the trucks and the storage tanks and the marina's gear, all add some water. But it's normally not a problem for us at that level. Unless over the years, it settles out to the bottom of the tank where it can corrode the tank itself or provide some nice environment for biologicals, which is the main part of that crap in the bottom of the tank. It's one of the reasons why Grand Banks and any other boat with steel tanks needs to have them replaced eventually.

So, where does this "crud" come from. Does it form over time or is a result of diesel being pumped into the tank unfiltered?

NewbieFromNJ said:

So, where does this "crud" come from. Does it form over time or is a result of diesel being pumped into the tank unfiltered?

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The answer can be both.

Or at least improperly filtered.

I see there r primary and secondary filters. Is there any such apparatus out there on the boat that would filter the diesel before it gets into the tank and I'm not talking a simple strainer.

NewbieFromNJ said:

So, where does this "crud" come from. Does it form over time or is a result of diesel being pumped into the tank unfiltered?

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I know nothing. Most of this is ignorant conjecture. Your best course of action is to simply not read the following. If you do chose to read, keep in mind that it is at your own peril.

It has always been my understanding that most of the problems with diesel fuel come with water contamination. When water is present, microbes can start to breed in the fuel. As they die their poor dead bodies create a sludge layer at the bottom of the tank. The best way to avoid it is to keep water out of your fuel. The best way to do that is make sure your O rings are in good shape in your fuel fills.

Once the microbes have gotten a foothold, it can be a problem to get rid of them. Getting the water out of the fuel is a good first start. This is where tank drains, water separators etc can be helpful. We all have good filtration systems to keep water and crud out of our engines, but few of us have systems that are designed (or effective) at "polishing" the fuel, ie getting the water out and filtering it really well.

If you have a big problem and your fuel is cloudy or changed color, then there may be a microbe infestation in the tank. Polishing wouldn't hurt, but if you do you really should try and clean the inside surfaces of the tank as well to remove as much of the sludge as possible. I would also hit the fuel with a large dose of biocide to kill off the microbes. That won't get rid of the sludge, but it will slow down its growth.

Then burn up that fuel as quick as you can by enjoying the boat. I would try to use it up and get the fuel level down as low as you are comfortable with. Then add a 1/4 tank of fuel along with more biocide and again use the boat a lot.

As others have mentioned, have plenty of spare fuel filters on board. It helps to have a vacuum gauge to be able to tell if your filters are beginning get clogged. It wouldn't hurt to review your filtration system as well to ensure that it is up to the challenge. Tony Athens has written some very good articles about it on the sbmar.com website. Even I can understand them.

Good luck and welcome.

NewbieFromNJ said:

I see there r primary and secondary filters. Is there any such apparatus out there on the boat that would filter the diesel before it gets into the tank and I'm not talking a simple strainer.

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Your problem going forward is not likely to be contaminated fuel. Think of it like a septic tank. A septic tank "works" because of active bacteria that break down the waste (their food). They need lots water to do their job. They also need to be kept healthy and happy. Your diesel tank may be like a septic tank now. Lots of microbes that are feasting on the fuel. All they need is a tiny bit of water. When you add more fuel, clean as it may be, you are simply adding more food for the microbes and a little bit of water since there will always be some water suspended in the fuel. You need to kill off and remove the microbes in the tank.

Buy a used Holley 'Red' electric fuel pump on EBay. Buy a used Racor. Buy a lot of fuel line. Close the tank outlet valve, disconnect engine supply line, connect new line, put other end of line into fuel fill, run all day. Voila, polished fuel.

If you have top of tank access you can use the output of Holley to wash the inside of tank, at least where baffles allow it. I bought a boat that had been on the hard for years, tank was full of water and sludge. Plugged filters constantly.

Now I have clean fuel, a spare fuel pump, and a spare Racor.

SoWhat said:

If you have top of tank access you can use the output of Holley to wash the inside of tank, at least where baffles allow it. I bought a boat that had been on the hard for years, tank was full of water and sludge. Plugged filters constantly.

Now I have clean fuel, a spare fuel pump, and a spare Racor.

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Nicely done.

Water and microbes also enter the tanks daily as the weather heats and cools. Like a lung. A warming tank exhausts air and a cooling tank draws in air. Air carries moisture and microbes. If your tanks are full then a very small amount of air is exchanged, but an empty tank exchanges much more air.
You have to kill the microbes and expel the water. Using a fuel conditioner that kills microbes and helps the primary filter to extract the water is how you defeat the sludge in the bottom of the tanks. There are 2 types of conditioner. One helps extract water and the other causes small amounts of water to be absorbed by the fuel and burned. I use the first type. If you have a primary like a Racor, Keeping track of how much water builds in the bowl is a good indication of how clean your tanks are. Mine rarely shows any water, but I use a conditioner all the time.
At your fuel dock, see if their filters are in plain sight. Either at the pump or tank farm. See if they're dated and it's in this century. Some filters have a bypass if the filter is clogged, so the engine doesn't stop.
I have cleaned black diesel (heavy contaminated) with nothing more than filters and a good conditioner and it burned fine. Probably less hp, but not noticeable.

I had my two 200 gal tanks 'polished' this fall. I'm told they ran the fuel in and out of the tanks and through their filters several times. Though we have access ports, they did not wish to open them; presuming there are transverse baffles there really would not be much point. $350.

I expected that we would have a problem since the boat was unmaintained for a number of years before we took her on. And, we had a couple hours with wind and chop on the beam last fall before we indeed had the problem a couple days later. Thus the polishing. I guess we'll have to go out in roly-poly-pitchy-sloshy conditions, preferably before we head up the NJ coast next summer, and see how fast we plug the Racors. At least I'll be able to service them in their new locations!

Asphaltines too.

"Asphaltenes in diesel fuels are becoming a much larger problem since the introduction of Ultra-Low Sulfur Diesel (ULSD) fuels.

There are actually several problems that have come together to cause the filter plugging black slime we so often see today.

Asphaltenes are highly polarized long chain components in crude and the heavier refined oils. Under certain circumstances these compounds associate themselves to form complex colloidal structures. In Low Sulfur Diesel (LSD – S-500), High Sulfur Diesel (HSD – S-5000) and heating and bunker fuels the higher aromatic content of the fuel tends to discourage the formation of the complex colloidal structures limiting the problem. However the EPA mandated reduction in aromatic content in ULSD has allowed this problem to happen sooner, more often, and in cooler temperatures than had been seen previously.

Asphaltenes agglomerate into an oily sludge. This problem is made worse when water is added to mix.

Petroleum and bio-derived fuels all hold water suspended in them, ULSD unfortunately holds approximately twice as much as the LSD and HSD fuels we had seen prior to June of 2006. Biodiesel (B100) can hold ten (10) times as much water as LSD and HSD, so even small amounts of biodiesel blended with diesel fuels dramatically increases the amount of dissolved water present.

Blending of fuels refined from different crude stocks further exacerbates this problem. Also, warmer temperatures in storage or due to the recirculation of fuel by the engine fuel system speeds the process and thickens the sludge.

Fuel that looks perfect going into a clean tank can develop tiny asphaltene droplets in a matter of hours when recirculation temperatures exceed 140°F (note: some newer engine fuel temperature as it exits the head exceeds 210°F). These pin-prick sized droplets can plug a 10 micron fuel filter in 3ooo to 4000 miles or less 50 hours of operation.

Many people mistakenly see this as a biological (bacteria and fungi) problem, however in the majority of cases the accelerated biological growth is the result of near perfect growing conditions that allows this rapid growth after the filter plugging asphaltene material has blocked the filter(s).

Keeping the water out helps, but the real solution is a stability additive together with a water dispersant."