diesel stored 2 years with stabilizer and biocide, should I drain and clean tanks?

[rslifkin]

Originally Posted by Simi 60

I'm a firm believer that water is caused by deck fillers and neglected O rings

I agree, any significant quantity of water will come from the deck fills or from taking on bad fuel. Condensation may give you tiny bits of moisture in the tank, but it's never going to amount to anything significant.

[JimZeigler]

It is my observation that my fellow boaters never fully find out how bad their tanks are fowled until they take the boat out on a rough day and the tanks get a good "stir." A lot of sludge will sit in the bottom of the tank and not be obvious until the wave action aggressively moving the fuel around. That said, it there is a lot of sludge, the filters will become fouled fast and you may require a tow back. Also, difficult to flush a tank in place because the baffles make it hard to reach the ends of the tank.

So, first of all, do you know if you have a problem? Have you fun the engine recently and detected water in your fuel filter bowl. That is the advantage of the Racor type filters assemblies - you can see the water in the bottom of the bowl. Install new filters, run the engine for several hours and see how dirty the filters become. Take a short run in choppy water and reinspect the filters. And as the others have said, install a polishing system. I built one with a Racor filter and a reefer fuel pump (refrigerated tailer truck trailers are called reefers) that I bought on Ebay. Has worked great. Also handle to refill the filter holders after changing filter cartridges.

[Timlich]

I too have a Volvo D2-55. My boat has been stored on the hardstand in Spain (very dry location) for 2.5yrs thanks to COVID. We put her back in the water in January and I’ve been running her on the old fuel (Tanks filled pre-COVID as we didn’t expect to be away so long!) both from stored in onboard tanks and also spare Jerry cans. I’ve had absolutely no problems with the fuel. I visually inspected the tanks before using and there was no evidence of diesel bug - just a very slight discolouring on the bottom of the tanks. I’ve sailed about 800 nautical miles since, and mostly in pretty rough seas so the fuel has been well stirred up. Still no problems. I suggest you use it up but check the fuel filter along the way.

[SuW]

I know this isn't easy for everyone, but having an inspection port in your fuel tank is very reassuring. Even if you can get an endoscope inside to look.

We bought our present boat when it had been sitting on the hard with 2 inches water over the floor, with an in-keel tank. The tank had a lot of water in it. (South part of Lake Champlain, NY).

The top of the tank is accessible, so we removed the inspection plate, pumped all the contents out (about 60L/15 US gal) into translucent jugs.

The contents were quickly distinguished between about half black/brown murky water that pumped out first, then fuel. Looking inside the tank there were a few small pools of black sticky material.

The jugs settled down - some were just dirty water, some separated into fuel/water, and some were clear fuel.

We cleaned the tank by hand and washed it inside with clean diesel. There were a few pitted areas - it's an aluminum tank.

We put the cleanest jugs of old fuel back in and filled the tank with fresh fuel.

Changed the filters. Engine started and ran well.

We keep the boat in Ontario. A few years later we opened up the tank again to look at the inside - it was clean. We don't appear to need biocide up here.

[lubogigi]

this is what I found after stalling in autumn winds, fuel was claughed up at the exit valve so bad I had to blow from the exit tube to inwards of the fuel tank.But this only made the engine work for a minute or two. I have Racor fuel filter and they didn't show how bad my tank were. Got back to port by bypassing the fuel line into a jerry can and made it home. cut a 5" hole on top of the tank and pumped all out into clear jugs, two where reusable 1/2 of the other was muck. Since then I added a second Racor fuel filter 5 micron (first was a ten micron) now the're in line, fuel goes through the 10 then the 5 then the one on the engine, its like polishing my fuel each time the engine works. Since then I cross my fingers and toes that this situation doesn't ever occur again (its really no fun to be stranded and left to the elements.) hey but all went well. still love sailing.
Photos show what was left in the bottom once the tank where emptied with a 3/4 inch fuel pump (amazon), which is permanently on board now ( I also use it to transfer fuel from jerry cans to fuel tank at sea without having to move the jerry can from its storage)no back strain, no spillage, no mess. Last photo is the tank cleaned, cleaned by hand ( also with a raged stick, tank is triangular shaped) to be sure all was gone.

[Cheechako]

2 years isn't too bad. But take a look at your diesel anyway. Even with biocide it can be quite cloudy and full of growth. (dont ask how I know!)
maybe the growth was in there and the biocide just killed it, leaving the debris, in my case.

[David Mathis]

Last year, one of the Caterpillar 3126 engines ran rough, soon lost power, then quit and would not start. The other engine ran fine. The mechanic found the fuel tank feeding the problem engine clogged with algae. It was so thick that it plugged the fuel pick up. The Racor vacuum gauge was in the red. Several filter changes had been made. The tank was pumped revealing fuel that looked like chocolate syrup. The other tank? The fuel was ruby crystal clear and the inside of the tank looked new. It seemed odd that one tank was clean and the other so contaminated. The tanks were always filled at the same time so the chance of getting bad fuel in one but not the other was eliminated. The boat is used for about 1000nm per year so having the same fuel in the tanks for an extended period is not an issue. Any guesses?

[rslifkin]

Originally Posted by David Mathis

Last year, one of the Caterpillar 3126 engines ran rough, soon lost power, then quit and would not start. The other engine ran fine. The mechanic found the fuel tank feeding the problem engine clogged with algae. It was so thick that it plugged the fuel pick up. The Racor vacuum gauge was in the red. Several filter changes had been made. The tank was pumped revealing fuel that looked like chocolate syrup. The other tank? The fuel was ruby crystal clear and the inside of the tank looked new. It seemed odd that one tank was clean and the other so contaminated. The tanks were always filled at the same time so the chance of getting bad fuel in one but not the other was eliminated. The boat is used for about 1000nm per year so having the same fuel in the tanks for an extended period is not an issue. Any guesses?

Slight leak from a deck fill o-ring maybe? Got a little water, dirt, etc. in there and it started growing stuff.

[Timlich]

Originally Posted by lubogigi

this is what I found after stalling in autumn winds, fuel was claughed up at the exit valve so bad I had to blow from the exit tube to inwards of the fuel tank.But this only made the engine work for a minute or two. I have Racor fuel filter and they didn't show how bad my tank were. Got back to port by bypassing the fuel line into a jerry can and made it home. cut a 5" hole on top of the tank and pumped all out into clear jugs, two where reusable 1/2 of the other was muck. Since then I added a second Racor fuel filter 5 micron (first was a ten micron) now the're in line, fuel goes through the 10 then the 5 then the one on the engine, its like polishing my fuel each time the engine works. Since then I cross my fingers and toes that this situation doesn't ever occur again (its really no fun to be stranded and left to the elements.) hey but all went well. still love sailing.
Photos show what was left in the bottom once the tank where emptied with a 3/4 inch fuel pump (amazon), which is permanently on board now ( I also use it to transfer fuel from jerry cans to fuel tank at sea without having to move the jerry can from its storage)no back strain, no spillage, no mess. Last photo is the tank cleaned, cleaned by hand ( also with a raged stick, tank is triangular shaped) to be sure all was gone.

Great idea with the fuel pump for the transfer from jerry cans. It’s a real struggle to do this at sea and a job I hate. I’m crossing oceans and it’s rarely calm enough to do the job cleanly even with a siphon. I’ve tried everything including hand pumps but for some reason my brain never considered an electric transfer pump! Even though I have one for polishing my diesel in a loop from the main tank! It just goes to show the value of sharing knowledge on these platforms. Thanks again.

[s/v Jedi]

Originally Posted by Timlich

Great idea with the fuel pump for the transfer from jerry cans. It’s a real struggle to do this at sea and a job I hate. I’m crossing oceans and it’s rarely calm enough to do the job cleanly even with a siphon. I’ve tried everything including hand pumps but for some reason my brain never considered an electric transfer pump! Even though I have one for polishing my diesel in a loop from the main tank! It just goes to show the value of sharing knowledge on these platforms. Thanks again.

Here’s my post from 2006 describing our fuel system, of which pumping from a drum (or can) is one of the options.

It even allows running from a jerry jug, with both pickup and return hoses into a jug.

https://www.sv-jedi.org/sv_jedi/2006...fuel_syst.html

[walt41]

Buy a 12-V fuel transfer pump and some hose for about $50 and attach to engine side of the filter, with discharge back to the tank and running off the battery. Change filter element as necessary. This will "polish" the fuel after a couple of hours.

[bclaude]

As many of us, my boat was stuck in the Caribbean for 20 months due to COVID. I had filled my 250 Gal tank to the brink before I left and added the right amount of Biocide. Sailing the Caribbean does not take that much fuel meaning that in the Summer 2021 I was back in the Med burning 3 years old fuel. I have installed a fuel polisher made of a RACOR filter with a 10 Micron filter in it. The fuel line to the engine has a 5 micron filter on it and the on engine filter is a 2 micron. In the end I had zero issues. I opted to use as much of my old fuel as possible before refilling. My engine is a BMW based YANMAR 6BY with common rail fuel injection. Much has been said about how sensitive common rail injection is to clean fuel which made me nervous. I wonder if some of you have an opinion on wether old fuel could be good enough for a traditional Diesel engine but not for a common rail. My experience leads to the conclusion it makes no difference but the experience of others would be welcome.