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Old 04-30-2012, 01:29 PM   #21
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RT,
that may work. pouring water over it would work but kind of a mess I have enough water in the bilge as it is. I would think just a spray bottle to mist the tank would do the job.
You sparked the ol light bulb thanks for the suggestion..

SD
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Old 04-30-2012, 04:03 PM   #22
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Greetings,
No problem Mr. SD. A rag soaked in ice water would probably cool the "empty" section of your tank sufficiently. The reason I suggested ice water is to increase the temperature differential.
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Old 04-30-2012, 04:57 PM   #23
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Greetings,
No problem Mr. SD. A rag soaked in ice water would probably cool the "empty" section of your tank sufficiently. The reason I suggested ice water is to increase the temperature differential.

RT - To expound upon your expeditious cooling-temp differential theory (a good one if I may add); then in a diametrically reversed temp actuation mode - - > warm palm of one hand against the tank with gun in other hand should in matter of short order be able to reveal the true line of fluid level... Ya think??
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Old 04-30-2012, 05:03 PM   #24
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That would work for cold fluids. Me thinks.

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Old 04-30-2012, 05:56 PM   #25
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That would work for cold fluids. Me thinks.

SD
Ya, mest too! Like cold fluid... fuel, water, and waste tanks.

I'm a gonna buy me a goost one o' dem dere hotsie-totsie guns and try er out next time wifie andst mes B ups dere at our precious liddle Tolly-boat!

I figure if my hand won't to the temp trick then I bet a hair-dryer reveals the fluid line temp difference to the gun likity split!!
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Old 04-30-2012, 07:29 PM   #26
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Come on, fess up Art, you're buying it for your next party!!
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Old 04-30-2012, 07:50 PM   #27
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The four saddle tanks in our boat have sight gauges. The day tank has an electric guages at the helm consol. Fuel return will change the temperature of fuel in a tank but I believe Art has gas engines so fuel return is probably not an issue.

I'd be pretty skeptical of depending on the tank temperature to measure level. The temperature is going to vary all over the place regardless of level with ambient temperature outside the boat, the temperature inside the boat as a result of the sun heating up a deck over the tanks, the engines heating up the space the tanks are in, and so on. While there may be constant ratios that can be determined over time you would have to take accurate measurements for every known condition.

While the idea of trying to find a level of liquid by using the temperature difference between metal with fluid behind it and metal with nothing behind it makes some sense on paper, it's the nature of temperature to even itself out. So if you measure a difference at all, it will probably be spread out over a significant distance. So where will the level really be? Right where the temperature starts to change, right where it stops changing, somewhere in between? And a level change of just a few inches can mean a difference of ten, fifteen, twenty gallons or more depending on the size of your tanks.

It will interesting to hear what you find out but it's not something I would want to make any fuel-remaining bets on. Either get an accurate electric gauge--- they exist although they're probably not cheap--- or install sight gauges. But I'm betting that using the temperature difference system will be just as vague as the gauges you have now.
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Old 04-30-2012, 09:04 PM   #28
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jleonard - You figured me out! Crafty guy you!! What fun I had... My younger days were exciting... to say the least! Heck, these days ain’t too shabby!! lmao

Marin - I've noted that liquid filled containers sweat pretty much exactly at and below the fluid level line under certain temp and humidity conditions. Meaning that the container’s temps above and below the fluid line can become notably different, due to certain temperature circumstances.

Sooo... stands to reason if a sudden broad space (18" elevation +/-) temp alteration is actuated upon tank’s exterior surface by waving a hand held hair dryer up and down for 30 +/- seconds, that spans and heats both the fluid filled level and empty airspace level, that the tank portion with fluid will dissipate its temp very quickly compared to the portion with just air. Therefore, I hope to find the capability of the gun to register that temp variation change and enable me to “come close” to seeing if my gauges are getting floozy or not.

I’m only doing this as a simple way to see if I need to go to the expense and task of putting in brand new tank level monitors. Due to obligations here it will be a while before I get opp to go out on boat and try this method. I’ll post here with what I find. Bet someone might experiment with it before me – ya never know! Some seem to already be itching to learn the outcome... it’s a “speriment”
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Old 06-18-2012, 12:33 AM   #29
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Infrared Gun Success!

After engines have run for about an hour, supplying considerable heat to our engine and fuel tank compartment... Infrared Temp Gun works well for accuratly checking fuel level (as a comparison to our fuel gauge readings) in our two 100 gal aluminum tanks that are outboard positioned alongside each engine. Each tank’s air filled area's aluminum exterior surface reached approx 12 degrees f warmer than the staying cooler fuel filled area. I could quickly determine within one half inch the actual fuel level. Each tank’s temp (on Gun’s temp screen) would notably change as I slowly passed up and down at the fuel level. I also found that by holding the gun’s nose directly against the tank provided the best accuracy; holding it away skewed the gun’s temp readings and made it more difficult to determine actual fuel level. For accuracy, I marked side of gun at the line where the infrared actually shoots – I found that the infrared line is not where to laser light line is positioned, at least not on my gun.
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Old 06-18-2012, 12:53 AM   #30
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Sounds like a good solution. Do tou think it would work equally well on tanks made of other materials? Iron, fiberglass, plastic?

Our four stainless saddle tanks have calibrated sight gauges so no problem determining fuel levels. But for tanks without them your IR gun method sounds like a problem solver.
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Old 06-18-2012, 07:46 AM   #31
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Fluke and Snap-On will certainly be pricey - probably worth it if they form part of the tools of your trade (or if you just like very nice tools). For testing tanks and a/c outlets, you might consider something by Craftsman or even Harbour Freight at a fraction of the price. I have a cheap one for checking exhaust elbows, a/c's and the like. It has worked well for the last 3 years. I believe I read somewhere that these things all work on the same principle, although the quality of manufacture may vary. I'm guessing that the most likely cause of failure would be leakage of corrosive goop from dead batteries.
I had a Craftsman. The first one failed quickly and was replaced under warranty. The second lasted a couple of years.

I decided to try something else and bought the "top of the line" model at Harbor Freight for about $30.00. It's been fine.

If I used one in my work or was working on critical systems, I would probably buy a better known brand. For casual use, the cheap ones seem to do the job.
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Old 06-18-2012, 07:54 AM   #32
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RT - Being a coast-living Atlantic Ocean boy from ages past, my preferred marine fuel gauge is a straight wood stick with volume notches implanted by knife blade... sticks are more accurate (every time) than any other item could be; besides maybe a clear glass tank with no schmeg stuck to its interior sides - LOL!

But, alas... the "new" boat makers (mine's a 1977 - and fairly new to me!) figured their "high tech" (automotive copy) in-tank mechanical gauges would make every lazy boater happier than hell! That is till they ran out of fuel some day with the ageing gauge still reading 1/4th full! So... with their great new mechanical fuel reading gauge available the “smart” (spelled s-t-u-p-i-d) boat designers decided that gave them license to place the tanks and fill hose at angles so that NO straight stick could possibly ever be used to “accurately” check fuel levels for making sure their super stupendous mechanical fuel gauges were not telling a fuel level fib!

If the world simply adhered to KISS – what a relaxing life it would be!!
The other side of your story is, in some cases, having a straight shot from the deck fitting to the tank so a stick could be used to measure fuel level would mean that the deck fills are not easily accessible for actually filling the tanks.

I can fill both my fuel tanks (one on each side) from the cockpit. I have to pull the water hose through the cabin and fill the water tank on the side that's away from the dock through an open cabin window. I would not want to do that with a fuel hose.

Boat design and construction is a series of compromises.
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Old 06-18-2012, 07:57 AM   #33
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For fuel, water, or waste tanks: To determine a tank material’s temperature differences at its fluid level...
As often happens, this thread seems to have gone off on a tangent, but if it's your thought that measuring the temperature at different points on the outside of your fuel tank will reveal the fuel level, devices to accomplish this are already available for propane tanks. Stick on strips that change color. Check your local home center or even Walmart.
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Old 06-18-2012, 08:02 AM   #34
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Having installed float sensors and experiencing failure in short order, I reverted to the Mark I Mod I dipstick method of determining fuel level. No moving parts, simplicity in itself.
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Old 06-18-2012, 08:56 AM   #35
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Sounds like a good solution. Do tou think it would work equally well on tanks made of other materials? Iron, fiberglass, plastic?

Our four stainless saddle tanks have calibrated sight gauges so no problem determining fuel levels. But for tanks without them your IR gun method sounds like a problem solver.
Don't know for sure on other tank materials... but probably the same law of physics should take place with any container type that had air space and a fill level of fluid space. One increment of necessity seems to be having considerable heat added to local ambient air around any tank, and in relatively short order too... such as in an engine compartment’s increased heat due to engines running. Our tanks' broad sides sit about 18" separated from each engine's outside edge. I checked twice after running for one hour each time and each time there were days between engines running so the temps of tank air/fluid levels had time to stabilize. In the case of my boat's fuel tank to engine close proximity layout, I believe if engines were run for many (say eight hours) the tank's fuel may gain more heat that makes the air to fluid heat differential less notable. Similarly... if engines just run for couple minutes the temp differential would probably not be as pronounced.

PS: – I purchased IR Gun off EBay at very reasonable cost. Works well.
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