Make sure your fuel tanks are clean ...

[Hesti]

We recently bought a boat from the early 1990's. As is the case with many many many boats, the tanks had never been cleaned (we had asked on all boats we inspected and the answer was always the same). We had the tanks opened (cut open, inspection hatches now installed), inspected and cleaned. There was some sludge in the tanks and quite a bit of water as well. Both could have caused trouble underway if it had been stirred up in a seaway.

[wolfgal]

yuck and thank you for the image, hadn't ever seen those kind of aliens close up

tell me, do you know how often a tank needs to be cleaned?



wolfgal

[Hesti]

Regarding inspection frequency, I can only guess. The boat is about 25 years old and that is what 25 years have left in the upper tank. The lower tank also had silt, but little to no water. The pre owner did not have any trouble yet as far as we know, but he did not move the boat in open waters, so little wave action to stirr things up. In our case, I guess inspection every 4 years should keep us out of trouble, for other uses and other areas, ..., that may well be different.

[wolfgal]

so this is actually silt and not organic (bugs)?

yes, i imagine that where we fuel up makes a huge difference.

that said, i've read so many stories about bugs in the system. it makes me wonder if organic growth is much more common than we'd expect

in any case, every four years sounds like a good rule of thumb. thank you



wolfgal

[GarthGregory]

In Croatia/ Greece for a number of years I had no problem with the growth of Algae in my diesel tank , then one year it blocked the filter and stalled the engine in a dangerous position . It took an enormous effort to get the Roto moulded tank out and clean . Since then I have never filled up with diesel without putting in the required amount of an additive .I currently use an Australian product called Fuelset which works well . Dirty diesel seems to be unusual in Greece or Croatia , but Algae seems to be a risk .

[Singularity]

Certainly opening up the tanks and washing them out is cleaning, but I think a prime dependent question is "what constitutes fuel polishing?"

As I understand things:
-biologic growth is the culprit here
-biologic growth cannot happen without water (one report stating as little as 40ml per liter will support growth)

So if/when people fuel polish without removing water...as I see things...then they are only effectively "mowing the lawn." When there is no water, there can be no growth.

On an intimately related note...the return line from the engine dumps heat back into the tank, increasing the relative growth rate inside the tank (that may be occurring). Use of a day tank circumvents this heated-fuel-grows-stuff-better phenomenon (at least in the main tank(s)).

[NorthCoastJoe]

When I got my Pearson 30 the first time I looked into the tank it was bad. Pumped out 10 gallons of fuel mixed with all kinds of goop. The original tank was monel that I changed to a plastic tank and placed it in a mount that makes it easy to remove without moving anything else. In the future if i think it needs a cleaning I can remove it for cleaning. The big failure on the original was that the fill fitting sat on the cockpit floor only protected by a "O" ring. The new filler is up where there is less chance of water and dirt getting in. Looking for a larger boat I think about how hard will it be to remove the fuel tanks. For my peace of mind I want them to be easy to remove.

[jharding]

I had a few close calls with stirred up crap in my dirty tanks. I put on an extra prefilter before my dual racors. nothing helped until I opened up the tanks and cleaned them, they looked like a swimming pool that hadn't been cleaned for years, at least an inch thick crud that I sucked out with a bent copper tube and clear line so I could see what was coming out to my prefilter. after "vacuuming" and then getting in with a scrub brush and scrubbing clean, letting settle and "vacuuming" again, did this several times until I saw clean white fiberglass tanks. I am very careful when fueling up and always run my fuel through a baja filter so I can see and catch any debris and water. Not getting any water in and putting in the proper amount of fuel additive I believe is the key to clean fuel system. My tanks are still spotless 8 years later. It is reassuring when motoring in a storm and I look at my racor bowl and it is clear and clean, and the engine doesn't skip a beat.

[crazyoldboatguy]

You could insure that the fuel you put into the tank is as pure as the driven snow and still have problems later. The issue is what happens when the tank is half full and goes thru a daily cycle of warming and cooling in warmer parts of the woror.

During the daytime as the air in the partially full tank warms, it expands. As the day cools off in the evening, the air contracts, bringing fresh air into the tank. Included in that is moisture and fungus spores. That is the source of the problem.

So, easy fix - keep the tanks full, right? But if you are at anchor in a remote spot with a partially full fuel tank, what do you do? Waiting for the problem to appear will likely result in plugged filters at a very bad time (is there a good time for your engine to quit?). Fuel additives help but don’t really address the issue - they mask it. It may take some time for the problem to rear its ugly head but when it does.....

The solution is a separate circulatory fuel polishing system that processes fuel at a much faster rate than your injector fuel return will. A fuel polisher like this one.

Gulf Coast Filters, Inc. Specializing in Bypass Oil filters, Fuel filters, Hydraulic filters and Custom filtering

[tworail]

This won't be news to anyone who has been through it, but owners of older boats with questionable tanks should take note. Not just failing tanks but design-wise as well...

When I removed the 1979 era diesel tank, it did appear somewhat clean on the bottom, however, once I started pulling it more apart there was an area in the tank that was baffled and completely inaccessible to clean or get to with your hands. There was at least 1" of sludge in that area all by itself and not really anywhere else in the tank. It would have been next to impossible to get rid of this sludge. If you can't get to all areas of the tank you should expect something like this (i.e. the worst) and deal with it accordingly.

[Delfin]

Originally Posted by wolfgal

yuck and thank you for the image, hadn't ever seen those kind of aliens close up

tell me, do you know how often a tank needs to be cleaned?



wolfgal

If the fuel is polished, and no external water leaks, probably never. I inspected mine after 15 years and there was essentially no contamination. 750 gallons each.

[Pete7]

Originally Posted by tworail

It would have been next to impossible to get rid of this sludge. If you can't get to all areas of the tank you should expect something like this (i.e. the worst) and deal with it accordingly.

Indeed, I had to use a 2" steel wall paper scraper to clean my tank. Fuel polishing did nothing to help despite regularly doing it.

Pete

[Dockhead]

Originally Posted by wolfgal

. . . tell me, do you know how often a tank needs to be cleaned? . . .

From once in 20 years to once in 2 days, depending on the fuel, the weather, etc.


In short, it's not possible to make a rule of thumb. I used to have my tank cleaned professionally every two years (at a cost of almost £1000 a pop), as I'm paranoid about fuel, having previously cruised in diesel-bug ridden Florida, but eventually realized that since the tank was always squeaky clean, never a speck nor a drop, it's not necessary in my particular conditions.



I would say you should have a good look inside your tanks no less often than once a year, and clean them if you ever see any visible dirt or water, but continuously keep a sharp eye on your filters (use dual Racors with the glass bowls), and if you see the slightest change in anything, pop the tank and inspect it.



Avoiding biodiesel like the plague is also important.


Better than all of this is to use a day tank -- which my next boat will have.


Some people swear by fuel polishing setups -- surely won't hurt anything, but I doubt that this is a real substitute for normal tank inspection and normal cleaning.

[Dockhead]

Originally Posted by crazyoldboatguy

You could insure that the fuel you put into the tank is as pure as the driven snow and still have problems later. The issue is what happens when the tank is half full and goes thru a daily cycle of warming and cooling in warmer parts of the woror.

During the daytime as the air in the partially full tank warms, it expands. As the day cools off in the evening, the air contracts, bringing fresh air into the tank. Included in that is moisture and fungus spores. That is the source of the problem.. . .

I think that's actually been busted as a myth. MaineSail did empirical tests and found no moisture being brought into a tank from "breathing".


And if you think about it -- moisture would only get condensed out into the tank, if warm moist air were breathed in and then was cooled. But a tank breathes the opposite of that -- it breathes out when it's warm, and in when it's cool.


If it breathes at all. This will vary according to boat, but my fuel tank is deep within my engine compartment far from the hull, and it doesn't actually change temperature at all between day and night. I've measured it. So in my case, the tank is not even breathing anyway. YMMV.



My Father taught me to always keep the diesel tanks full. But I think it's actually not good practice to do this -- the fuel ages and absorbs moisture from the air, especially over periods when the boat is not in use. I use my boat more or less all year round, but much less lately in the winter, so I tend to leave the tank closer to empty over the winter, so I can bunker fresh dry fuel in the spring. Has been working very well for me last 10 years.

[a64pilot]

You should never have to clean your Diesel fuel tank.
If you treat every gallon of fuel that ever goes into it, you will never have growth in it.
ALL fuel has water, dissolved in it ,every bit does, we used to measure how much was dissolved in Jet fuel with what is called an Aquaglow test kit, if it exceeded standards, then the fuel was recirculated in the fuel truck until it met standards, the fuel truck had a trashcan sized filter, that had I was told the same granules that are in baby diapers, that absorb water and turn to gel, recirculating through that filter would dry the fuel
https://www.gammontechstore.com/Prod...Code=GTP%2D322
Your not doing that in any boat fuel polisher I have heard of.

In fact every boat polishes it’s fuel, the engine only burns a small amount of the fuel pumped, the majority goes back into the tank and is recirculated.

You can however get alsphaltanes in your fuel that can precipitate out in your tank, but I think ULSD is much less likely to do that. In fact unless I’m mistaken over time ULSD will dissolve Asphaltanes and clean your tank, it’s sort of like Ethanol gasoline in that respect it has a solvent property, or so I have been told, but I’m no fuel Engineer either, only know what I have been told and read.
Asphaltanes your not polishing out, they have to either be ignored, or physically removed.
I believe the number of boats that inspect and clean their tanks is at best a small fraction of the boats out there, and yet we don’t see stranded boats often with clogged filters.
My boat sat most of its life, it accumulated about 500 hours in 27 years, I did have funk in the fuel, had to remove and clean the fuel dip tube many times on delivery. However it worked itself out, I treat every gallon of fuel that goes into the tank.
I cannot inspect my tank, not without removing the sole, which would be a very big job.
I’ve only clogged a couple of filters total. And haven’t in a couple of years, I change filters yearly, just preventively.

Ask any OTR truck driver or bulldozer operator or Farmer how often they remove and clean their fuel tanks, and I guarantee you they will look at you like your crazy.
It’s letting untreated fuel sit for long periods in tanks that causes problems, and I don’t think ULSD stores as well either.
I know for decades after WWII there was still Diesel from WWII still being used