Replace the diesel or not??

[fox9988]

I'm burning fuel that sat at least two years before I bought the boat. No problems after 10 hours run time.

[Icarus]

Originally Posted by Annabel

I hope this is in the right forum. We are returning to our yacht in Greece after the extended time of 2.5 years because of Covid (Grrrrr) we are a bit worried that our diesel may have developed a bug problem. My husband is rather convinced that we should empty the tank and replace it with new diesel. Any views on this anyone? Thank you

The diesel in my boat has a 2nd tank with 12 year old fuel in it...about 100l, i added some bio fuel cleaner and the fuel is clear.
In your case I would change the fuel filters, add some fuel treatment, have a look at the fuel and carry on.
2½ years is not long.

[bil56]

it all depends where the fuel comes from
in several European countries, there is a percentage of biofuels that favors the development of bacteria (in addition to the lower sulfur content)
if you really have a large amount of diesel in your tank, put an active dose of additive, check your filters, and cross your fingers...
I repeat, Total for example, only guarantees its diesel for 6 months...

./.

[Shaneesprit]

You don’t need to replace it, but if you are worried get a pump a water trap and a fuel filter, and filter it yourself - the process is called polishing.
Fuel should be pumped from the bottom of the tank and returned to the middle of the tank, although if your boats in the water the sea movement will mix the diesel anyway.
Depends on how much fuel you have, you can run this for a time period or pump to and from another tank.

[Annabel]

All the info you have all given is wonderful. I'm just wondering if I am allowed to ask if anybody has had dealings with Super Diesel Lefkas. Or maybe someone has a recommendation for someone in this region who would come to Preveza Is the diesel polishing a fairly straight forward procedure for a diesel mechanic?

[Dieseldude]

Originally Posted by Icarus

The diesel in my boat has a 2nd tank with 12 year old fuel in it...about 100l, i added some bio fuel cleaner and the fuel is clear.
In your case I would change the fuel filters, add some fuel treatment, have a look at the fuel and carry on.
2½ years is not long.

Great that your 12 year old diesel was ok. But every situation is different. The presence or not of water in the tank is probably the most important factor. The interface between any water and the fuel is where fuel microbes grow. Does the tank have a drain at its lowest point? Just drain out a few liters and see how it looks through a clear container compared to fresh diesel. If dark and sludgy you probably have fuel microbes. As someone noted, any bio component in diesel can increase the potential for microbe growth.



If you do not have a well placed drain, the next best indication is to get some water paste and smear it on the sounding tape or sounding stick. Sound the tank and note any change of color that would indicate water. If no water indicated, you can be reasonably confident that there is no fuel microbe. If water is present, it would be prudent to take a sample and have it lab tested.



I've been aboard a ship in a severe storm that had fuel microbe growth in the tanks. The exaggerated roll in rough seas will stir up the bio sludge that would normally stay in the bottom. It is tiring and stressful to be up for hours past normal watch to constantly clean pre-filter strainers and change filters. Losing propulsion to a clogged fuel system when you need to maintain a heading in foul weather is a risky situation. There is no guarantee that you will be able to work the sails, and no guarantee that the sails and rigging will remain in tact. Clean fuel and a reliable engine can keep you alive. Another consideration is if you have a modern common rail engine with electronic injectors, they are much less tolerant of dirty fuel and water.

[sail sfbay]

[QUOTE=Annabel;3607363]............Is the diesel polishing a fairly straight forward procedure for a diesel mechanic?[/QUOT

Diesel polishing is a big deal, requires a lot of equipment and generally not performed by a marine diesel mechanic, based on my experience in the San Francisco Bay. I only know of one marine diesel fuel polisher in the San Francisco Bay. If you want the fuel polished find a qualified local marine diesel fuel polisher with references.

You have a 58-gallon fuel tank so that is a lot of fuel to polish and you need to have 2 connections to pull and return fuel. Do not forget about the risk of a fuel spill during that operation, unless you are going to contain all the equipment and fuel on the boat. If it was my boat I would try to sample it first (multiple samples) to see if you have algae growth issue OR just burn it. Worst case, if you burn it, you MIGHT plug your primary fuel filter, which is easily replaced.

[Annabel]

Originally Posted by 2 Itchy Feet

Great question that has been puzzling me as well. We have a full tank in a 2019 catamaran but didn’t put any biocide in at the time as we thought we would only be 6 months till next use. 2.5 years later I am wondering about this. The marina tech people said a year ago it was too late to put biocide in, so I am apprehensive!!!
If your boat is in Cleopatra Marina and you are there first week of May, look us up. 2 Itchy Feet, FP Astrea 42 currently on the hard but will be wet for a couple of days.

You may be on your way before we get there, not due until 26th May. I wonder what decisions you have made after reading all the information provided in this thread. I contacted Cleopatra, couldn't get a fuel polish until end June, so must be a lot of people in the same boat, no pun intended. I have located a diesel mech in Lefkas who could do it I think. Have no clue as to how we could get into clean the tank if we got to that one. Just really excited to be returning to our mythical yacht

[Dieseldude]

Originally Posted by Annabel

You may be on your way before we get there, not due until 26th May. I wonder what decisions you have made after reading all the information provided in this thread. I contacted Cleopatra, couldn't get a fuel polish until end June, so must be a lot of people in the same boat, no pun intended. I have located a diesel mech in Lefkas who could do it I think. Have no clue as to how we could get into clean the tank if we got to that one. Just really excited to be returning to our mythical yacht

If your tank is not accessible for cleaning, perhaps just pour in enough hot water mixed with degreaser detergent to cover the bottom to a depth of a few inches. If you have an air compressor available, the wash water can be agitated with air. Make small holes in a length of tubing that has a plug in the free end, and submerge in the water. Will need barb to air QD fitting and hose clamps. Rig a valve to control air flow and connect the compressor hose. The bubbles will create turbulence that can be just as effective as hand scrubbing. Does not require much pressure, maybe 20 PSI would do it. The tubing needs to be heavy enough to sink. If plastic, attach some weights. After letting it stand a day or overnight drain it or pump it out or use a wet shop vac. Then rinse with plane hot water, and drain. The tank will need to be dried out by circulating air with a fan and flexible ducting.



With the washing, you will have a few gallons of oily water to properly dispose of. Scrubbing or air bubbling is not practical,the best that you can do is to dose the tank well with biocide upon refilling. Not ideal, as it is best to get all the algae and sludge out. But if the biocide does its job, the fuel algae should not grow back. You may need to change fuel filters before normal interval though.