Diesel tank clearing

[sarabande]

Hoping to complete purchase soon of a 35ft m/sailor which hasn't been really used for 4 years or so. There appear to be THREE diesel tanks of about 80 gals each, and they all seem to be half full.

Is it prudent to drain and refill these tanks in case of gunge or biological contamination, or is there any way I can test the diesel output to see if it's nice and clear ?

 

[BAtoo]

Look in your water separator & see what it looks like. Also syphon some from each tank. Sounds like engine is drawing from all 3 at once so they all run out together!! Would probalby run each one individually so you know where you are....

 

[Birdseye]

Without doubt, the prudent thing to do is to drain and clean. Diesel gunge lives in the bottom of tanks along with the water / oil interface so quite often it wont be apparent in the filters etc until it is stirred up by bad weather ie just when you dont need that problem. With a motor sailer, when you might not be able to sail out of trouble, play safe.

And all diesel (and petrol for that matter) has the bug in it so it would be a miracle if tanks left half empty for 4 years didnt have some.

 

[Twister_Ken]

Odds are if the boat has been unused for 4 years with parially full tanks, almost certainly there will be water contamination via condensation, and if there is water present a goodly chance that some form of diesel bug is present at the diesel/water interface. Try draining or siphoning from the bottom of the tanks, to see what comes out. I suspect it won't be diesel as we know it. There are diesel cleaning services available, but I suspect it's not likely to be economic for your quantities.

For peace of mind, I'd be inclined to drain all three tanks, change all filters, etc, and refill with clean fuel, plus a heavy shot of biocide.

 

[chas]

I had a similar problem with a boat that had not been used for five years and had diesel bug. There was only one tank but it was a pig to get at. Suggestion was that I dosed it with Soltron and fitted a Racor pre filter, got myself lots of filter elements and motored as much as I could for a bit. The theory was that the diesel would be circualted through the filter and much of it back to the tank. It worked but was a bit tedious - but was easier (and probably cheaper) than acessing the tank.

So I would suggest that if you can get at the tanks easily, clean them out. If it is difficult try the method above.

 

[cliff]

Check to see if there is a sump and/or drain point on each tank then if so drain off the crud, gel, bug until you see "clean" diesel coming out dose with a biocide and use the fuel. Alternatively if you have inspection hatches on the top of the tanks, open one and pump the fuel across into another ½ empty tank then clean out the bottom of the tank. Once that is done pump the fuel from the other ½ empty tank in to the one you just cleaned and clean out the second tank. finally pump fuel out of the last tank into the second tank and clean out the last tank. Do try not to stir up any sediment when transferringthe fuel between tanks. You should now have one tank clean and full, one tank clean and ½ full and one empty. fill the empty tank with fresh fuel and dose the other two with biocide or something like "Fuel Set". Fit two filters in parallel with a set of change over valves and away you go. <u>IF</u> you pick up any crud in one filter you can switch over to the other filter and change the filter in the other at your leisure. Do ensure you also clean out the fuel lines before fitting new filters. £2.50X120 gals = £300 and you have the problem of disposing of 120 gallons of fuel which will be quite useable.

Above is based on past experience doing same job on a boat with 5 tanks and approx 1600 gallons of diesel that had been lying in the tanks for at least 8 years.
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[pappaecho]

I had the same problem for a boat which I bought 2 years ago, was 28 years old with a 44 gallon stainless tank.

The best thing is get the tank out clean it and the steam clean it. In order to do this I used a succession of 25 l drums which I filled from a small diesel proof pump. I sucked out the last few gallons with a Peta oil extractor ( engine oil etc) and then removed the tank which was not easy.
Having removed the inspection plate when the tank was out of the boat I found very little in the way of general gunge, but not knowing its past, it was impossible to predict the outcome.
I filtered the contents of the 25 l drums having allowed then to settle, using the same small pump to remove the good oil from the inevitable water in the bottom of each drum.

If you dont want the hassle of doing this to three different tanks, I would try one to start.. If it is reasonably free of gunge I would take the risk of fitting two prefilters/water separators in parallel, just like the Lifeboats do, which allows a rapid switch to the reserve filter whilst the blocked one is cleared.. and leave the other tanks as is. Obviously you would need to work out how the three tank system works, to ensure that the input feed to the engine goes via the duplicate filters in parallel. There was an interesting article on such a few months ago in PBO, with input from the RNLI, who attend regular breakdown due to blocked filters

 

[crwber]

Its probably not a bad move to clean them all! It will be a pain to do so, but at least you know exactly what condition you are starting with re the inside of your tanks. i Have just been through a similar experience..took the lazy route only to find my fuel lines blocked completely. We were positioning our boat mid-renovation and were lucky to be able to use tide and wind to return to our mooring (no deck fittings so were not able to sail). Whilst you are at it, consider fitting inspection ports and decent drains...will be worth it in the long run