How much diesel in fuel tanks over winter?

[Frank Langer]

As I live about 1,000 miles from where I moor my boat (that will change when I retire), I always need to think ahead for maintenance work and upkeep, as I don't always know when I will get there again.
My question: I will not likely sail from October through March, and want to do what's best for my diesel fuel/motor. The boat will stay in the water in a temperate BC, Canada climate (though still around freezing temps on occasion, but the water won't freeze). I had planned to leave the fuel tank full to minimize condensation, add biocide and fuel stabilizer, but someone recently advised that I empty the tank completely instead. I am leery of that, as that would mean running it to the bottom, perhaps sucking any debris on the bottom of the tank into the system and causing worse problems.
What would you all suggest?
Thanks,
Frank.

 

[dcoyle]

I am the 2nd owner of 82 E33 in Maine. The po gave me his winterazation process and I have used it successfully for 3 winter seasons. The fuel tank gets topped off, stabilzer, not biocide, is added. So far the engine starts right up in the spring. Hope this helps.

 

[therapidone]

ditto

We keep ours on the Chesapeake, and she's been in the water (and it has frozen) as well as on jacks for the winter...top it off, add the additives...starts first time, every time (so far).

Regards,

Ed

 

[u079721]

One thing to keep in mind...

I used to top my tank off just before hauling out. But two years in a row we had diesel comming out of the vent just prior to relaunching. Turns out that with the boat on the keel there is enough of a downward tilt to the boat (which also helps remove rain) that the fuel in the full tank was tilted toward the vent. As soon as it warmed up and the fuel expanded we had a leak out the vent.

After that I would bring the tank up to about 7/8 or 15/16 full - never full. You also wouldn't want fuel to be standing in the filler line.

 

[Frank Langer]

Dcoyle, why no biocide?

I am the 2nd owner of 82 E33 in Maine. The po gave me his winterazation process and I have used it successfully for 3 winter seasons. The fuel tank gets topped off, stabilzer, not biocide, is added. So far the engine starts right up in the spring. Hope this helps.

Dcoyle suggested adding stabilizer but no biocide--can you explain why no biocide? Is there something in the stabilizer that also does what the biocide would normally do, or is there another reason not to add biocide? Do most people regularly add biocide to diesel fuel throughout the year?

thanks,
Frank.

 

[ted_reshetiloff]

I use Biobor only and have had good luck. On the other hand if I could easily empty the tank completely and clean it out each year for the winter I would. If the tank had an access port and you could get in there you could easily wipe it down with a little oil to keep corrosion away for the winter. Diesel no mater what you treat it with is not stable for very long. I'm no engineer but thats what I have been told and read. A little moisture in the tank is no big deal if you run a good racor type filter separator. Draining and cleaning the tank on my boat is just not an option right now. Ultimately I want to downsize my tank from ~55 gallon to maybe 30. I just dont need that much fuel or weight.

http://www.hammondscos.com/fuel/biobor_jf.html

 

[Shadowfax]

I also fill the tank, add stabilizer and biocide. I fill the tank to prevent condensation, the stabilizer to protect the fuel as it sits for 6 months and the biocide to make sure the creatures are kept at bay while the tank sits for that long. I have never had a problem and I change fuel filters every year in the fall and check the filter bowl after running the engine for a few hours in the spring to make sure water or creathers have not made it into the tank anyhow. I also make sure the O ring that seals the filler cap is togeather.

 

[CaptnNero]

Fuel tank extract

We purchased our E34 in October 2004. This spring the fuel filter was becoming restricted immediately after sailing in some rough seas and the rpms dropped about 10 percent. After investigating, I decided to siphon all of the contents of the tank. I say contents because when I peeked into the sump area of the tank I saw significant precipitants which were definitely not fuel. After emptying the tank I also sprayed a few clean gallons back in to rinse and re-emptied a few times.

The photo is of the precipitants that I settled out of the 12 gallons from the tank in my own polishing process. This concoction smells like paint thinner instead of diesel. The precipitant layer of sediment and water at the bottom of the photo is about one pint deep. It does not include the gunk from the bottom of the Racor bowl which was half full of precipitants nor a few more grams of solids filtered through several layers of paper towels. For the year that we owned the boat before this we have been using a treatment containing a biocide.

I originally called a few local fuel polishers, but I was givien estimates of $350-450 and service times of close to a month. Hence, I decided to do my own polishing, and in fact one of the polisher companies recommended that I do it myself.

As a result of this experience I decided to let the tank level drop before the winter shutdown. Then I will empty the tank and tape the vent shut to prevent moisture penetrating over the cold winters we have. The fuel that I empty will be dumped in with our heating fuel which I have been told is compatible.

In the spring I will be adding only fresh fuel to the boat. Before I refill the boat tank next spring I will examine the inside of the tank and report on my findings.

 

[Frank Langer]

neal, how do you peek into the sump part of the tank...

Neal, thanks for your post. As I think my fuel tank is entirely sealed, except for the hoses, how do you "peek into the sump part of the tank" to inspect and clean it? Is that a special modification on your boat?
So far, I have had no problem with the engine/fuel in our "new" boat, but I understand diesel is quite finicky, and I want to do everything possible to avoid water or dirt or biological contaminants.
thanks,
Frank.

 

[CaptnNero]

How do dey do dat ?

On the late 80's E34 the fuel sender is several inches from the sump area. To get better access I removed the liner under the bed. Then I removed the fuel sender and leaned in very close with a smalll bright penlight to peek inside at an angle towards the sump. The sump area is obvious since it's right under where the fuel lines attach. You need to get the level pretty low before you can actually see well through the fuel. For siphoning I put the hose through the fuel sender opening and aimed it under the fuel pickup.

I think a more straight forward way to proceed for quality assurance purposes involves removing the fuel pickup tube which does not reach the bottom of the sump. Then you can carefully place a longer siphon tube through the fuel pickup tube openning straight down into the very bottom of the sump to sample it's contents (that's where the sediment and water end up) and siphon out until it runs clear. On the E34 the sump is not a separate depression but just the lowest point at the front of the tank right at the crease that represents boat centerline in the bilge.

Whether you remove the fuel pickup and siphon a little fuel there or siphon all of fuel out as I did from the sender openning, the fuel system will have to be bled after re-filling.

If the under bed liner wasn't removed, I don't know if one could get close enough to the fuel sender opening to see in, but maybe it's possible.

Ideally there should be a separate tube for drawing from the sump. In fact Nigel Calder has this in his fuel tank diagram of his mechanical and electrical book. This winter I will be removing the fuel tank to either replace it with a plastic one or have it coated so that hopefully I'll never have to deal with the dreaded fuel tank leak. I will also make sure that there is another openning above the sump so that I can easily drop a siphoning line in there to monitor quality and remove contaminents easily. BTW-small airplanes I have flown in have sump sampling access under the tanks which are in the wings.

Neal, thanks for your post. As I think my fuel tank is entirely sealed, except for the hoses, how do you "peek into the sump part of the tank" to inspect and clean it? Is that a special modification on your boat?
So far, I have had no problem with the engine/fuel in our "new" boat, but I understand diesel is quite finicky, and I want to do everything possible to avoid water or dirt or biological contaminants.
thanks,
Frank.

 

[Frank Langer]

Thanks, Neal.

Thanks, Neal. That makes good sense. Now I'll have to decide whether to go to the trouble to undo lines, etc. in order to take a look into the tank to see if it's clean (boat was new to us this spring), or to assume that all is well as long as the motor runs well. Nigel Calder stated in his book that he follows the principle of not fixing something that isn't broken, but I tend to want to be a bit more proactive, though I have at times created a problem by doing so.
Thanks again for your reply.
Frank.

 

[CaptnNero]

proactivity

In your case I recommend removing the fuel pickup tube and doing at least a sampling siphon there. As for Nigel Calder, he recommends having sump access for sampling and cleaning anyway. I think an old fuel system tends to be partially broken (contaminated) most of the time unless you're really on top of it. It only takes one rough seas voyage to plug the filter with that hidden crud. There was enough crud in my 1988 tank to plug the $30 primary filter many times over.

Whatever you decide, good luck !

Thanks, Neal. That makes good sense. Now I'll have to decide whether to go to the trouble to undo lines, etc. in order to take a look into the tank to see if it's clean (boat was new to us this spring), or to assume that all is well as long as the motor runs well. Nigel Calder stated in his book that he follows the principle of not fixing something that isn't broken, but I tend to want to be a bit more proactive, though I have at times created a problem by doing so.
Thanks again for your reply.
Frank.

 

[Frank Langer]

Thanks, Neal. This board sure is a great source of information!
Frank.

 

[dcoyle]

I dont use biocide because the previous owner said he didnt use it. Im not sure this is accurate but my thought is that whatever the biocide kills will sink to the bottom of the tank and eventually make a nasty sediment pile. If something is alive in the fuel wouldn`t the 3 filters clean it out? My process has worked so far, although last year I did overfill the tank and found fuel in the bilge. I cleaned that up sveral times before it the lightbulb went off that tank was still too full. I drained a cup or so out at electric fuel pump and was fine. I`m interested in comments about biocide.

 

[CaptnNero]

One of the fuel polisher pros I talked to said to be careful with biocide. His theory was that the biocide kills the biologicals and they precipitate instead of remaining suspended and being caught by the filter or passing on through and being combusted.

I dont use biocide because the previous owner said he didnt use it. Im not sure this is accurate but my thought is that whatever the biocide kills will sink to the bottom of the tank and eventually make a nasty sediment pile. If something is alive in the fuel wouldn`t the 3 filters clean it out? My process has worked so far, although last year I did overfill the tank and found fuel in the bilge. I cleaned that up sveral times before it the lightbulb went off that tank was still too full. I drained a cup or so out at electric fuel pump and was fine. I`m interested in comments about biocide.

 

[CaptnNero]

overfilled = leak ?

I would be concerned if your overfilled tank leaks. Perhaps your have a loose fitting or worse yet an old leaky hose.

I have a friend with a 2002 Nauticat 32 that leaks when filled into the fill tube. I tightened the fittings but I don't know if that totally fixed it.

I dont use biocide because the previous owner said he didnt use it. Im not sure this is accurate but my thought is that whatever the biocide kills will sink to the bottom of the tank and eventually make a nasty sediment pile. If something is alive in the fuel wouldn`t the 3 filters clean it out? My process has worked so far, although last year I did overfill the tank and found fuel in the bilge. I cleaned that up sveral times before it the lightbulb went off that tank was still too full. I drained a cup or so out at electric fuel pump and was fine. I`m interested in comments about biocide.

 

[rwthomas1]

Diesel fuel is more stable than gasoline by a wide margin. There are far fewer aromatics to evaporate off over time. Worrying about condensation, why bother? It only should be an issue if you are using a lot of fuel with large swings in temperature to cause a condensate problem. With a partially filled tank in a static situation there is little or no exchange of air so the existing air will condense become dryer and thats it. Any decent filter will deal with condensate moisture. Add a little fuel conditioner like Howes Lubricator Diesel Treat and maybe some biocide if you have had a microbe problem. If your fuel system has been microbe-free then don't worry about it. Once you have microbes then periodic treatment is a good practice. The biocide may kill the microbes and they may precipitate or get caught in the filter. This is better than leaving a microbe problem untreated. I have seen very large filters on big powerboats go black in minutes, repeated hour after hour until the gunk was all gone from a major infestation. To me the best solution would be to run the tank down to near empty, up to a 1/4 tank or so before storage. The treat before storage and top off with fresh fuel at the beginning of the next season. Why pay to store fuel all winter? Why burn last years leftover fuel for most of next season? The longer a volume of fuel sits around then the more likely you will have a problem. RT

 

[Shadowfax]

Biocides

dcoyle,

First I think the reason you found fuel in your bilge is that one of the hose fittings is loose, or the seal to the inspection port / fuel sending unit is not sealing correctly if you have one in your tank. These are easily checked.

As to biocides: The idea behind biocides is obviously to kill the critters that like to live in diesel fuel. It stands to reason that if your tank is contaminated and they are not being killed by the treatment, then they will flourish without a biocide and turn your fuel tank into a 27 gal spawning environment for the beasts. The debris that I remove from the bottom of my filter bowl I would describe as film like and cleaned out with a paper towel. I have seen Racor filters completely clogged from living microbes

I have had my tank “polished” once. This process was nothing more then running the contents of the tank through some filters a number of times and back into the tank. They did not clean the tank, they polished the fuel. The people doing this work generally work on tractor trailers that turn a tank of fuel a couple of times a week from storage tanks turned maybe once a week. I fill my tank maybe twice a year from storage tanks of unknown quality and filled who knows how long ago with who knows what growing in them; which is why I use biocides.

I dont use biocide because the previous owner said he didnt use it. Im not sure this is accurate but my thought is that whatever the biocide kills will sink to the bottom of the tank and eventually make a nasty sediment pile. If something is alive in the fuel wouldn`t the 3 filters clean it out? My process has worked so far, although last year I did overfill the tank and found fuel in the bilge. I cleaned that up sveral times before it the lightbulb went off that tank was still too full. I drained a cup or so out at electric fuel pump and was fine. I`m interested in comments about biocide.