We've been transferring fuel from our jerrycans into our main fuel tank with a shaker tube and a filter funnel.  It takes a bit longer, but it's well worth the effort.

TLDR: here's what the setup looks like:

Setup to Transfer Fuel without Spilling

What you'll need is pretty simple:

  1. Oil absorbing pads
  2. Fuel Filter and Water Separator Funnel
  3. Shaker Tube
  4. Biocide (Optional, but recommended)

Oil Absorbing Pads

We bought a bail of them (100 sheets) a year ago, we still have a lot left, and they've been very useful.  The brand we got was the Brady SPC Basic Oil-Only Heavy Weight Absorbent Pad from Amazon for about $30.  They not only come in sheets, but each sheet is perforated (this is important).

Brady SPC Basic Oil-Only Heavy Weight Absorbent Pad, White, 15" L x 17" W (100 Sheets Per Bale) - BPO100 

A Water Seperator and Fuel Filter Funnel

The brand we bought is called the Mr. Funnel AF3CB Fuel Filter, from Amazon at about $27.  Find out more at the Mr Funnel website, but for some reason, the Amazon product page for it is better organized.

When we had just bought Petrichor, we were having a lot of engine stoppages.  It turned out that the fuel in the tank was both dirty (bottom of tank gunk) and a lot of water had collected in the tank (likely due to condensation, from fuel docks, etc).

Mr. Funnel AF3CB Fuel Filter

This one in particular was selected because it has a flow rate of 3.5 gallons per minute.  This is important because we want to make sure that we don't get into a situation where we're pouring fuel into the funnel faster than the fuel will get filtered.  Here's an image for how it works:

How the Mr Funnel Works. It traps dirty and water in a sump, and allows fuel to filter through the center.

Consider it a pre-filter for your fuel system.  You can be sure that the fuel going into the tank is free of dirt and water.  Your water separator and racor filter (10 micron) is next; and then the fuel filter is the final piece that'll ensure clean fuel is going into your engine.

Running the tank empty (woops) was one way to remove all the gunk out of the tank but it also meant having to replace the fuel filters and water seperators a few times.  It was a bad mistake on our part, but it also had the side effect of cleaning our diesel tank to a better state.

Shaker Tube

We've found that using a shaker tube to transfer fuel from a jerrycan to the funnel is the way to do it.  There are so many devices that claim to prevent spillage, but I've found them to always be quite annoying in that they not only do not work as advertised, but the design themselves are horrible.  First, though, here's the shaker tube we got, the Hopkins 10801 FloTool Shaker Siphon with 6' Anti-Static Tubing.   Again it was off of Amazon for about $15.

Shaker tube with a brass end that has a glass bead

It's generally a bad idea to use your mouth to start a siphon with a tube.  I've done it once in an emergency, it tastes bad, and I'm sure it wasn't good for me.  This thing is much better.  It has a bead in the brass part that seals to prevent backflow, but easily "floats" open when there is liquid flowing past it.  The shaking action (up and down) pulls a little fuel at a time until it starts the siphon for you.

This shaker tube has a flow rate of 3.5 gallons per minute.  The Filter funnel also has a flow rate of 3.5 gallons per minute.  The shaker tube's flow rate is actually closer to 2-3 gallons per minute in our experience, but that's ok!  I want it to be slightly slower than the filter funnel.

What this means is that once it starts, you can transfer a 5 gallon jerrycan in a couple of minutes.

To go back to no-spill spouts on jerrycans, they just simple do not work.  The main reason for this is because they all are connected to the jerrycan themselves.

These spouts are junk. They never work as intended and I've always spilled fuel when using them, regardless of how careful I am.

Here a quick diagram of how most jerrycans and their spouts work:

Diagram of how jerrycans work.

In the diagram, you have:

Yellow - This is the jerrycan itself.  They typically have a capacity of 5 gallons (~ 35 pounds when full).

Black - This is the spout.  They all generally have some type of notch that you have to push against to open the spout.  Some are spring loaded, others have a ratchet design.  But they all work on the same principle: You have to apply pressure against it to open the spout.  The intent is that if there's nothing pushing the spout open, it'll automatically close.

Green - This represents the fuel.  The stuff you want.

Blue - This represents water.  Diesel floats on top of water.  You don't want this in your tank.

Brown - Solid other stuff.  Definitely don't want this.

Gray - This is a small air tube.  It's supposed to prevent glugging by letting air in.  In practice, this thing never has a high enough flow rate to match the fuel's flow rate.  Once you reach a certain point (about 1/2 to a gallon in), a vaccuum forms inside the jerrycan.  This tube allows air from the outside into the jerrycan in order to "push" the fuel out.  The flow rate of air through this tube is the limiting factor.

On the left is how everything looks when the jerrycan is sitting upright.  On the right is how everything settles when you're using the spout to pur fuel in.

Looking at when you start pouring fuel in, you'll notice some problems:

  1. You have to lift the entire jerrycan.  At 7 pounds per gallon for diesel, that's 35 pounds to start.
  2. They often times will "glug".  This means you're holding up that jerrycan for 5-10 minutes while it slowly glugs out.
  3. You're depositing the dirt and water first.
  4. Difficult to terminate flow.  You have to release pressure in order for the spout to close.  If it's even half full, that's still about 20 pounds.  And you have to disengage the spout from the fuel deck fill, so if fuel is still flowing, you'll most likely spill some fuel.  Sometimes, they get stuck in the open position.
  5. Requires downward pressure to open valve.  When you pass a certain point (about 2/3 empty), there isn't enough weight in the jerrycan to keep the spout open.  So now you have to push down.
  6. You can't see what's coming out of the spout.  So you can't be sure what's going in the tank.
  7. There's a handle at the top of the jerrycan, but when you invert it to pur fuel out, the handle is pretty much useless.
  8. This is very difficult to do if not impossible with choppy seas.

All this adds up to almost always spilling fuel.  And, especially with point #6, with a shaker tube, you can see exactly what's going into the tank because the tube is clear.

If you need to stop fuel flow with the shaker tube, simple kink the tube or pull the tube out of the jerry can.

You can also sit the jerrycan upright the entire time, so no need to lift anything or push anything.  Just hold the tube in the tank right above where the bad stuff is and you'll minimize sucking in dirt and water.

There's no glugging with the shaker tube... just a nice solid stream of fuel.

The filter funnel will take care of the rest.

Biocide (optional)

This is optional, but it's also the best time to add some biocide to your fuel.  Diesel is, in essence, a specific type of refined oil.  There's a reason why you can put vegetable oil into a diesel engine and it'll work - and bacteria love it.  Just like how cooking oil can go rancid, so can diesel.  Biocide is there to inhibit growth and fouling of your fuel.

We use Biobor JF that we get from the church of West Marine.  It's $50, so not cheap.  But you also don't need much.  The 32oz bottle is enough to treat 2560 gallons.  Our fuel tank is 30 gallons.  So that means one bottle is good for 85 fill ups or 512 jerrycans.  A bottle of this stuff should last you all year.  Don't cheap out now, get the good stuff.

Why we recommend doing it while you transfer fuel is because you can be sure that you're putting in the right amount (I've yet to see a fuel gauge on a fuel tank that tells you exactly to 0.25 gallons how much fuel is in there) and not over doing it.

If a jerry can is 5 gallons, you only need to add 1/16 of an ounce per transfer.  If it's the first time ever adding biocide to your tank, just double the amount to 1/8 of an ounce.  Here's the recommended amounts:

You don't need much of this stuff.

The act of transfering the fuel will also ensure proper mixing.  When you simply pour it down the deck fill, you can't be sure it got into the tank.  The stuff is pretty viscous, so there's a good chance some of it just stuck to the tube going from deck fill to tank.

Putting it All Together

OK!  So now that we have all of our parts and materials, we can start putting everything together.  You can add the cost of a jerrycan too if you want (new is about $35), but we just got them from a swap meet for $5 a pop.  So initial outlay comes to between $127 to $157.

The setup looks like this:

  1. First, add your biocide to a jerry can.
  2. Sit the jerry can somewhere about 6 inches above the deck fill.  In our case, our cockpit has a raised area around it, so it makes it easy.
  3. Take a sheet of absorbant pad.  One sheet should have a perforation down the middle to separate it into two.  Don't tear it apart.  Instead, make a small hole in the middle.  Place this pad over the deck fill.  This will capture any fuel that may drop out.
  4. Place the filter funnel through the hole in the pad and into the deck fill.
  5. Insert shaker tube (metal parts) into the jerry can as far down as you can, but above any water or dirt that you should be able to clearly see inside.
  6. Start shaking the tube a bit.  It'll quickly pull fuel into the tube and the siphon should begin.
  7. Sit and wait.  You'll hear the ball in the metal part start to jiggle around once you get close to the end.
  8. Once the jerry can's been emptied, pour the leftovers either back into the jerry can or into a separate container for disposal.  This is the stuff you don't want.
  9. Optional: this is a good time to measure and take note of how much fuel is in the tank.  We have a dipstick where we measure inches of fuel.  You can now get a very good feel for how much fuel is in there, because if you do a before and after, you can now make a chart for how many gallons per inches of fuel... since you're adding 5 gallons at a time.
  10. When complete, use another oil absorbant pad to wipe up any remaining fuel.  We store everything in ziplock bags with extra pads to absorb any extra fuel.  It keeps it all neat and tidy.
Oil absorbing pads all over the place to ensure we capture any fuel leftover for storage. We use heavy duty bags so that they last and are reused as much as possible.

Hope that helps and happy spill-free fuel transferring!