What is fuel bugs or diesel bugs? How to get rid of them, and how to avoid them coming back.

What have I done to avoid the fuel bugs or diesel bugs to get back?
Let's see what happened to this motor sailor, a Nauticat 38.The boat is rather old, its 40 year old, but in good condition and with a new engine 4 years old, and almost a 1.000 hours. The condition of the fuel tanks are unknown at this time.
The first trip of the year was early, perhaps a bit too early. It was 5 hours motoring. At the end I felt that the engine was not performing well. It did not stop, but it was not quite as it used to be. So, safe at my destination I checked the fuel filter. Then I was terrified. It was almost completely blocked by dead fuel bugs. Dead or alive…??
Have a look at this water separator. The fuel should be clear and green. Now it is just a brown mess.Luckily I was moored to a pier, but I was still 5 hours away from home, and the weather had changed. I did not dare to go back. I had to call the ghost busters. Or at least the fuel bug busters.
Fuel bugs or Diesel bugs are a microorganisms that grow on fuels. They feed on the hydrocarbons in the fuel and create biomass, biofilms and damaging by-products. These microorganisms live in even the smallest amounts of water, often from condensation, and at the interface of fuel and water, where they can create thick biomass.
So, I had to call the bug buster. He arrived with some impressive equipment. All the fuel was removed from the tanks. We have 2 tanks with 300 liters of fuel in each tank. The fuel was cleaned, and later put back on the tanks.He made three holes in each tank, to clean the inside of the tanks properly. Then the same procedure on the other tank. Here you can see how the tanks looked inside, before he cleaned it.
This is after he cleaned it.
It took half the day, and it cost a fortune, but I had no choice.Now I was ready to sail home again, and really start the season.
So, what have I done since that time, so I don’t get this back? First, I use fuel additives to kill the bugs.I check my water separator often, and I change my fuel filters often. Second, I remove the water. Since water is heavier than diesel, it will stay in the bottom of the tank. Several times during the sailing season, I drain some diesel from the tank, to get rid of any water. Here you can see how I do it. The black hose is just for safety, in case someone opens the valve by mistake. I remove this black hose.Temporarily I connect the short blue hose, that lead to a small bottle. Then I open the valve just a few seconds, to drain water and fuel.Now you can see green clear fuel.In the beginning I got remains of the bugs in one of the tanks. Here you can see the fuel from port and starboard tank. Look at the difference.
Now after some time, I get only green clear fuel when I do this. Now I do this some times a year just to be sure there is no water in the fuel. Then I sleep so much better!
Yacht: 1982 Nauticat 38 - S/Y Maja
Bug buster: fuel-service.no/
Photo equipment: iPhone 15 Pro Max + Insta 360
Editing: iMovie on a MacBook Pro
Narrator and editor: Jarle Karlsrud

[@glennchartrand5411]

In the American Midwest farmers call it H.U.M.bug Hydrocarbon Utilizing Microorganism It doesn't just get into Diesel fuel , it also grows in hydraulic and engine oil.

[@Sailing-Maja]

Nasty stuff!

[@sportsmancraft1]

Don't have refueling points horizontal and flush on the deck especially in the scuppers. Install a bigger filter and spare new filters onboard.

[@Sailing-Maja]

@@sportsmancraft1 Totally agree with you.

[@rossr100]

We had this in a Cummins emergency generator years ago. When the Mech' told me I thought he was having a joke! No joke.

[@Sailing-Maja]

@@rossr100 No joke. Not at all!

[@RichardCummins-ni4em]

Desiccant dryers for fuel tank vents are cheap and easy to make, silica gel bags can be obtained for free or close to free from motorcycle dealers and if placed in a canister inline with incoming vent air will remove atmospheric moisture. Lay bags on the deck on a sunny day will dry them out. That said, I agree with henroshipping, no shortage of contaminated fuel out there.

[@skunkjobb]

I tried to install that a couple of years ago but the damn vent connections are impossible to reach without removing the tanks and then I first have to remove the engines so I gave up. Otherwise, it's a good idea.

[@Sailing-Maja]

Interesting. Never heard about them, but understand the principle. Have you tried it? Does it work? I assume you need to change them often or dry them in the sun often. Desiccants will absorb moisture all the time when exposed to humid air.

[@RichardCummins-ni4em]

​@@Sailing-Maja Hello Sailing-Maja. Yes I have made and used them to good effect. Silica gel will indeed absorb moisture if left out in a humid atmosphere, however inside an essentially sealed desiccator can they will only pull moisture out of air that passes through the can. That air volume will be equal to the volume of fuel used so relatively little in practice. The motorcycle crate silica gel I have used consist of approx 500gm cloth or perforated heavy paper bags, I draw fuel tank inlet / vent air from the bottom of the canister via a neoprene hose with the tip of that hose buried beneath several bags, atmospheric air enters at the top of the can, ie: air to the tank has to travel past and around several bags prior to entering the tank. In the tropics I reckon atmospheric air could be drawn from a dry area such as an air-conditioned saloon via said neoprene hose.

[@Sailing-Maja]

@@RichardCummins-ni4em Great. Thanks.

[@henroshipping]

Check where you get your diesel from, condensation will not give you that amount.

[@Sailing-Maja]

@@henroshipping I totally agree! When travelling around I get diesel from different places. One of these places must have been contaminated with this stuff.

[@skunkjobb]

@@Sailing-Maja Check the gaskets on the fill lids too. Mine were bad so I got rain water into the tanks.

[@Sailing-Maja]

@@skunkjobb Absolutely true. I have already changed the complete fill lids. They were 40 years old, so both the gaskets and the plastic lid were at the end of life time. Now I have new ones in metal, and with an O-ring that is easy to replace.

[@andrewdillon7837]

There was an aircraft crash on Mayday , where they got a decimal wrong and put too much bug killer in the jet fuel..

[@Sailing-Maja]

@@andrewdillon7837 Oh. That’s not good. You need to get it right.

[@andrewdillon7837]

@@Sailing-Maja kg vs pounds thing ,,i have every Mayday aircrash episode ,,,little things like metric are hard for some ppl

[@Sailing-Maja]

@@andrewdillon7837 We all go metric, foot by foot ….

[@andrewdillon7837]

@@Sailing-Maja So you arn't Inching away then,,

[@0e32]

Stop blend in RME into the diesel and the problem is gone!!

[@Sailing-Maja]

@@0e32 Nothing we users can do about that. We get get fuel we get, and we need to adapt. Apart from that, I do agree with you.

[@0e32]

@@Sailing-Maja In Sweden you can buy fuel without RME so called white diesel..I do so and dont acquires microorganism problems in my machines, boats, yachts, trucks ect. We sailing abroard a lot and never fill or tank directly from the pump, alwas in 20L plastic containers so the can sit on deck for a week and the diesel and water can layer up, then we fill our maintank by siphon and leav the "Blidge" water in the plastic container.

[@Sailing-Maja]

@@0e32 We buy without RME here in Norway as well, but nevertheless we got it. Dont know how, but we did get it. By the way, your routine is very good! 👍👍

[@stevethurlow9059]

Simple, install a Algae-x

[@Sailing-Maja]

Thanks. I’ll check that.