Filling fuel tank - when is it full....

[Scott T-Bird]

I feel no need to overfill the tank. I have an 11 gallon tank and fill only 5 gallons at a time from a 5-gallon can. When the fuel gauge reads less than 1/2, it's time to put in 5 gallons. It's a simple method based on relatively little use of the engine. If I was motoring for long periods to get somewhere, it doesn't apply. I'm a little surprised by the disdain for fuel gauges. I've never experienced any problems with them ... don't know what ya'll do to make them fail.

At the risk of thread drift ... for those that consider condensation a problem in the winter, why not plug the vent line over the winter? A closed system won't exchange air.

 

[Grouperhound]

Foaming

OK, really dumb question.

I don't trust my fuel gauge so I keep track of my fuel usage.

When I fill the diesel tank, it foams up so to prevent the foam from spilling all over the deck, into the marina, etc., I stop filling as soon as I see foam. It foams no matter how slowly I try to fill it.

However, how do know that I've filled the tank to max for the season? I do add treatment to it at the end of the season.

Should I assume the tank is full as soon as the foam gets close to the fill port?

Thanks.

I get a 'burp' sometimes which results in a foaming overflow, but the tank is not full. I don't think foaming is a good indicator of the tank being full.

I have a Maretron fuel flow meter that keeps track of my usage, and then I reset it after each fill. I watch the pump readout to know when I am getting close to what I used, then I listen. The Totalizer on the meter is incredibly accurate. During my last fill up I was within tenths of a gallon, quite impressing the dock hand. Unfortunately it is a rather expensive solution because you need two flow sensors for a diesel, plus the module to connect them. Finally you need a way to enter the calibration info for the meters upon installation. That being said, I love it. I actually use the GPH Flow Rate instead of my tachometer to throttle the engine. For example 1.4 gph is about 2400, 1.6 > 2600.. Knowing how much you are burning also has a psychological effect on how hard you push the engine, or not. You can also display miles per gallon if you so desire. Will it ever pay for itself? Doubtful, at least not during my ownership.

 

[JamesG161]

Overfilling....
1) I just replaced my sensor (in tank measuring device...WEMA brand...$54... all stainless steel)
2) I took all the diaper protections for spill control and very SLOWLY filled the 50 gallon tank and watched the fuel gauge marking every 5 gallon change after a 2 minute stop (gauges are damped to prevent changes in 4 foot seas).
3) On my gauge, full has wide blue area that turned out to be about 10 gallons or 20%. At first I thought OMG, then it occurred to me never fill more that 80%. Why? Waves and Spills.
4) I am never concerned, on normal use, until my tank is low. I yawn in between.
5) I still calculate fuel consumption by a good rule of 1 Liter (quart) per 10 HP used per hour. If you know your max rpm and rated HP then rpm is directly related to HP. For example: 40HP engine at 3000 rpm would be 20HP used at 1500 rpm. So running at 1500 rpm for 2 hours would 20HP x 2 hour x 1 qt/hr-HP = 4 quarts or 1 gallon diesel used. This is close but other conditions may cause this to vary. It is also a good engine/shaft/prop trouble shooter.

SO... Calculate AND get a good tank level device. Fill no more that 80-90%

Water and Condensation...

1) Unless you live in an area, like Washington State, were the relative humidity and dew point make it rain all the time OR have climate controlled fuel tank..

CONDENSATE IS INSIGNIFICANT....
OMG... DON'T EVERYONE JUMP OUTTA THEIR SEATS.... LOL

The opposite of Condensate is Evaporate...both happen... Temperature of tank versus dew point on your weather forecast. When tank is warmer than dew point... evaporation of water.

But But But....

Water sinks below the diesel... ah ha ... no evaporation... WRONG... Diesel has dissolved water and will evaporate that water and then adsorb water from bottom... Thus water will migrate from bottom to top. The amount of water in the air that condenses in maybe and teaspoon in a 40 gallon empty tank. Negligible in the fuel since all diesel fuel centers have the same problem as your fuel tank.

Remember if you get in 3+ foot seas you will emulsify the water with the diesel (at time you might need your auxiliary power)

So...
1) Buy a good secondary fuel filter like the Racor 500, which separate water, algae, and solids. Check the clear filter bowl for water which can be drained off bottom each time you sail.
2) Keep a couple of spare filters on board. Changing take about 10 minutes.

If you are really scared of water in diesel. Sample the bottom of you tank with a turkey baster with extended tube. Eject sample in a tall skinny glass and come back in a few hour to see you have separated water layer.

If you have a visible water layer on bottom then you may decide to add a popular emulsifier to your tank to suspend in microscopic droplet which may be separated by your Racor filter or harmlessly burn in you engine. Todays low sulfur diesel and oils have eliminated the water and Sulfurous Acid problems in combustion.

Jim...

PS: Two degrees in chemical engineerin 30 years experience.

 

[Patrick S/V Shangra-La]

I listen to my vent tube for the boat. It makes a great hissing sound as it fills. Once silent linstop and the tank is usually full.

 

[manada2]

I have a dip stick calibrated for 32 gallons. There is a T with a plug at the fuel return on the tank. When I fuel my boat I check the fuel level and fill appropriately. It works perfectly. I get a full tank without spilling or overflowing fuel.

 

[datasailor2]

Topping off the Tank

I never used a gauge, well I used a dip stick on my older boat but that proved unreliable. Now I just calculate how much fuel I have used (based on engine hours and RPM. Then listen to pitch of sound as air starts to pass out the tank when it approaches full. I have been filling tanks for over 20 years and can't remember ever getting a forming discharge. If I had a gauge, I would fix it

 

[NotCook]

Fill hrough the access hatch

We use only a dipstick to determine how much fuel we have in each tank, with a table for each tank to translate inches to gallons. For example, in our starboard tank, when it reads 32 inches, it has 287 gallons. While that is still 6 inches from the top of the tank, we consider that full, to allow for healing. Likewise for each other tank. When fueling, which we only do when we get somewhere below 100 gallons, we remove the tank access hatches and watch the fuel fill the tank until the -6" mark. We have no intention of allowing an overflow. The bigger problem for us is fuel getting several years old before we use it. So, depending on circumstances, we leave one of the 3 tanks completely empty so we aren't carrying 500+ gallons around to get old and its cetane.

As a pilot, I never trust a fuel gauge.

 

[Waybad]

For Foam,screw a 1 1/2 inch S.S. Groco hose barb with a Stainless steel tubing inside press fit, Long enough to about 1 inch off the bottom of the tank. I had my tube tack welded. For tank level you can buy Fuel rated clear heavy wall tubing. Put a Tee on the outside of your drain shutoff. compression fitting used on the tubing which extend up the side of your fuel tank. Very small opening at top. A small petcock type vale at the bottom so you can use it when needed only. You now have a visual of how full your tank is. I have a small piece of tubing on the top so I can blow the fuel back in the tank and not risk any leakage that could accrue. used for twenty years never ever had any problems.
Vent tube high up inside a station with whistle below deck. Good luck waybad

 

[Richard Dwyer]

I have tried every possible approach to filling the fuel tank. I have a 2003 426AC and this is what I have learned. If your fuel tank is located under the aft bed and is centered then the first thing to know is your tank is shaped like a wedge. It is approximately 14 inched deep near the sender and approximately 6-8 deep aft. This means that as the fuel is consumed the gauge moves slowly for the first half of the fuel burn and faster during the second half. In other words if you fill when the gauge is at 1/2 it will take more than 50% of the tank capacity. The fuel enters the tank AFT and if you over fill the tank you will probably notice the fuel tank will bulge. I used to fill the tank then add about 3 gallons more which I determined to not be a good idea once I felt the tank bulge. This also increases the pressure on the fuel sender gasket. So I suggest you slow the fuel entering the tank when at the fuel dock and listen to the air being released through the vent. As soon as you hear the air venting reduced, or see fuel foam, you will know the tank should be full. But remember this only works if you slow the fuel entering the tank

 

[JamesG161]

Richard, I have the same size/shape tank (Hunter 430) which gives you an non- straight line gallons vs. volume% relationship. When I have had a known near empty tank I have calibrated my tank with a new "curve".

1) Add in 5 gallon increments. Stop filling. Wait a few minutes to stabilize the fuel gauge
2) Record/plot total gallons added and tank gauge reading.
3) Put new calibration curve in Captain Log.

As I noted in my rant above, the 100% blue area on my gauge was only 80% full.
So I fill until 100% and the gauge "coasts" to about 90% actual volume.

I also carry 2 5gal yellow diesel cans full. The new diesel cans are designed to prevent overfilling of your fuel tank when pour/filling from the yellow cans.
Jim...