Fuel Spill

[skipmac]

Fuel overflow during refueling has been a problem in every boat I have ever owned. Sailboats or motorboats, large and small, gas or diesel it has been a problem with every boat.

When pumping diesel or gas into the tank when the tank reaches full, before the auto shutoff on the filling handle engages I have fuel gushing out of the fill pipe onto the hull or deck and into the water. Doesn't seem to matter if I fill fast or slow I get fuel blowing back up and out of the fill port. If I fill very slowly the spill is a lot less but still happens.

Now this has never happened with any car or truck I have ever owned, so why does it happen with all my boats? Is it just me or do others have the same problem?

So far the only solution I have found is to stop filling when the fuel gauge shows full but in my experience you are missing up to 10% of the tank's capacity when the gauge shows full. The other fix I have tried is to wrap a rag around the fill nozzle to seal the fill port but that is only partially effective and results in fuel blowing out the vent.

So anyone know the solution? Have I missed something simple and obvious that everyone but me knows about?


Skip

[shipofools]

this was an option I have seen, but it seems to have been discontinued.

No-Spill™ by Davis

[Shrew]

I've always used the theory that the tank should only be filled to approx 90% to allow for fuel expansion as (if/when) warms up.

[skipmac]

SOF - Thanks for the link. Even thought discontinued doesn't look like it would be rocket science to make a DIY version. Problem is, most of my spill is not coming out of the vents but the fill pipe, unless I plug the fill pipe with a rag. Then a lot comes out of the vent so would take a pretty large bottle to catch it all.

Shrew - According to my research, the expansion of fuel is pretty low. I calculated for a 40 degree F temp increase (pretty extreme) you would see about 2.76% expansion in fuel volume. On the other hand, with my fuel capacity of 80 gallons filling to 90% I would only lose 8 gallons but looking at that from another point of view, that's about 60 nm loss in motoring range.

To underfill is a workaround but it is a technical detail that does annoy me and just for the personal satisfaction I would like to know why it is a problem on boats and not cars, at least for me.

[nigel1]

Another solution could be Barton Fuel Whistle - Only £12.95 - Force 4 Chandlery

If you can mount it low enough down in the vent hose.

[osirissail]

In the USA they can get rather anal retentive about fuel spills and even require you to turn yourself in. To avoid this I installed the Racor Lifeguard in the fuel tank vent line.
See: RACOR-PARKER FILTRAT Filter at West Marine

Also I moved the vent from the outer hull to the sidewall of the cabin top. I keep several packages of "diaper liners" which are rectangular pads that absorb large amounts of any liquid. I use one or two just below the on deck diesel fill and keep a couple handie by the tank vent.

[skipmac]

Originally Posted by nigel1

Another solution could be Barton Fuel Whistle - Only £12.95 - Force 4 Chandlery

If you can mount it low enough down in the vent hose.

Have seen this or similar in the catalogs. Have you tried one and do they work?

But still this is just a workaround and not addressing the root cause. I'm curious as to why this happens in boats and not cars?

Do you, does anyone else have this problem fueling your boat?

Skip

[capn_billl]

It probably has to do with the shape of the tank coupled with the length of the fill hoses and vent lines. In cars the two are usually tied together. I just listen at the vent while holding a piece of quick-sorb over it. When I hear gurgle I stop. Usually a teaspoon or less caught by the towel.

[Captain Bill]

My experience has been that this problem is caused by an improperly vented tank. Boat builders seem to have a blind spot when running vent lines to fuel tanks. There is often a low spot in the line below the top of the tank which traps fuel either when filling or due to boat motion. This causes the tank to pressurize as it is being filled. The force of the fuel going into the tank overcomes the pressure for a while but eventually it overcomes the force of the fuel and spits back out. When you use the rag you block the pressure from coming out the fill tube and force the trapped fuel out of the vent line. It is also possible that the vent line and filler tube do not go into the highest part of the tank due to hull position which traps some air at the top of the tank which pressurizes and forces the fuel back out. If the fuel tank is not on the center line the act of filling a tank on one side of the boat can induce a small list and cause air to be trapped at the top of the tank. Make sure your filler tube and vent lines are as straight as possible and note their position in the top of the tank to see if a slight list will result in trapped air. I have a friend that has the problem of a vent line that cannot be run without a dip in it that traps fuel. He has come up with two solutions. He puts PVC fitting over the vent line and blows it out before fueling. The second solution is a long plastic tube that he fuels through that inserts into the filler pipe all the way into the tank. The tube is smaller than the filler pipe so the trapped air in the tank comes out around the smaller tube and is never trapped by a plug of fuel. Good luck.

[thinwater]

Second the Raycor Lifeguard. I works pretty well. Never have more than a teaspoon come out, even when I goof and fill it to the brim.

It is still required to have a good venting system, of course. And remember, many marine fills DO NOT have auto-stop features. Nothing will help but attention.

[David M]

When fueling I put an oil sorbant below the vent. My vents point inside the boat, not overboard. There is always a little fuel that trickles out.

The real trick for fueling is to put your ear near the fuel pipe and listen for the change in the sound of the fuel pouring. You will hear the pitch get higher as the fuel level starts coming up the pipe. When this happens I know the tank itself is full and I shut off the fuel nozzle before the fuel gets any higher up the fuel pipe.

[capt_douglas]

I can hear the pitch change as the tank fills. The sound of the air coming out and the sound of the fuel flowing down the tube changes, generally rising in pitch, in my experience.

I also have an approximate amount of fuel that I'll be taking and as I get close, I slow down the flow rate and listen carefully. I keep a number of absorbing pads close to the fuel fill and don't try to press the tank.

Some fuel tanks have secondary vents that can burp before the fuel comes out of the fill point so you have to be careful as you top off the tank.

[nigel1]

Originally Posted by skipmac

Have seen this or similar in the catalogs. Have you tried one and do they work?

But still this is just a workaround and not addressing the root cause. I'm curious as to why this happens in boats and not cars?

Do you, does anyone else have this problem fueling your boat?

Skip

Hi Skip, not tried this product but thinking about installing one, the reviews I have read are pretty mixed. At the moment I syill rely on listening to the fill pipe and have an oil absorbant pad held below the vent. I've found that by filling slowly seems to work best

[skipmac]

Thanks for all the comments. My theories on why this happens are about the same as Captain Bill's. But it is strange to me that it has been a problem on every boat I have ever owned.

From what I can tell, the main difference between boat tanks vs car tanks is that the flll line from cap to tank in a car is much shorter. I have never removed a car gas tank to look but it could also be that the car tanks have a shape that puts the vent and fill higher than the rest of the tank (sort of the opposite of a sump in the bottom of a tank or bilge) so air isn't trapped in the tank to force fuel back out.

I do try to listen for the change in pitch as the tank fills but have two problems. The worst is that my high frequency hearing is not what it used to be. I think too much rock and roll did me in. So if there is any ambient noise at all while I'm trying to fill then it's really hard for me to hear the sound.

Then the fill on my sailboat is on the deck so to hear it I have to bow down and lay my ear right on the deck. It looks like I am worshiping at the alter of diesel but maybe at my age I don't care that much if I look foolish anyway.

It also annoying when I get diesel in my ear.

[Capt Phil]

I used Capt Bill's method for years on a dozens of different boats, both power and sail. I only recall once having a dribble which was caught before it ever reached the ocean. If equipped with sight gauges, check level before fueling, check again after a few minutes to figure out fuel fill rate (this varies a lot from fuel dock to fuel dock, particularly outside the US), and time it to hit 90-95% of tank capacity. If you don't have a sight gauge, sounding tanks with a stick/ruler is another option. Running tanks down to less than 10% capacity, you risk sucking up some pretty nasty s--t into filters and lines... no fun to clean them out when you are outside somewhere. Vents have a bad habit of clogging up so good idea to have a few feet of pipe cleaner available to ream them out from both ends if possible. They are neglected on most boats. I have never trusted those auto shut off nozzles and wouldn't leave fuel running unattended into either a boat or a car... don't forget the biocide... cheers, Capt Phil