Those damn fuel gauges

[knotheadcharters]

We all know how inaccurate fuel gauges are on boats. Is there an accurate way to tell how much fuel is in the tank? I have 2 wing tanks that are slightly elevated and I am unable to access the top to dip them. (I used to do this on my last boat and never was in doubt about fuel level). I've tried the tap method but really can't be sure. Any suggestions?

 

[Art]

We all know how inaccurate fuel gauges are on boats. Is there an accurate way to tell how much fuel is in the tank? I have 2 wing tanks that are slightly elevated and I am unable to access the top to dip them. (I used to do this on my last boat and never was in doubt about fuel level). I've tried the tap method but really can't be sure. Any suggestions?

I suggest searching in archives via "search" button in this page's top bar. Many informative threads/posts exist.

Best Luck1 - Art

 

[hollywood8118]

We all know how inaccurate fuel gauges are on boats. Is there an accurate way to tell how much fuel is in the tank? I have 2 wing tanks that are slightly elevated and I am unable to access the top to dip them. (I used to do this on my last boat and never was in doubt about fuel level). I've tried the tap method but really can't be sure. Any suggestions?

FLOSCAN..

Floscan Instrument Co. Inc.

HOLLYWOOD

 

[mbevins]

I have one of these installed. It is amazingly accurate.

http://www.cruzpro.com/fu60.html

Sent from my Nexus 7 using Trawler

 

[knotheadcharters]

I don't need Flowscans I know my fuel burn, I just want to know how much diesel is in the tank. I don't trust that flowscans are anymore accurate from some things I've read.(garbage in garbage out, it is only as accurate as the calibration) The best way would be sight gage on the tank but alas not installed.

Art I'll search

I guess what I mean is I like to see how much fuel I have, not let some gauge guess. My tanks are slightly oval and I know how to calculate volume so for me I like it simple and mechanical not more electrical gadgets.

 

[psneeld]

You say you are going to keep the boat a long time in another thread...I would work towards some kind of sight gauge if possible....but that's up to the tanks and install configuration.

Are your tanks top or bottom feed?

Also the "stick" method doesn't require a solid object. On several USCG cutters I deployed on...they "stabbed" the tanks with a windup measuring tape and a plum bob on the end. Still not always convenient but thinking out of the box for some.

 

[knotheadcharters]

Top feed and only have a coupe of inches of clearance above the tank. Flex tape would work. I'll have to look into it and see if I have an access point like my old boat.

 

[Off Duty]

You say you are going to keep the boat a long time in another thread...I would work towards some kind of sight gauge if possible....but that's up to the tanks and install configuration.

Are your tanks top or bottom feed?

Also the "stick" method doesn't require a solid object. On several USCG cutters I deployed on...they "stabbed" the tanks with a windup measuring tape and a plum bob on the end. Still not always convenient but thinking out of the box for some.

Perfect! You took the words right out of my...well fingers
Done and used both, and both are simple, easy, and effective!

We used the sight gauges on the airboats. Work perfectly. (Just saw your response. Disregard the sight gauge idea.)

 

[Art]

You say you are going to keep the boat a long time in another thread...I would work towards some kind of sight gauge if possible....but that's up to the tanks and install configuration.

Are your tanks top or bottom feed?

Also the "stick" method doesn't require a solid object. On several USCG cutters I deployed on...they "stabbed" the tanks with a windup measuring tape and a plum bob on the end. Still not always convenient but thinking out of the box for some.

ps - GOOD Fn' idea... Duhhh... I could a had a V8!!! TY for sharing that little piece of CG genious!

I also like/trust direct stick fluid readings better than any other means. My tanks both have too much turn in filler hose from deck mount to tank... so that even a 3/8" dowel can't enter. NOW, thanks to your post, I'm gonna try rigging a fabric tape with svelt and non edged (so it can'y get hung up inside on anything in tank) plumb bob weight-end and try my luck!

Bravo - Dude!!

 

[kulas44]

Head pressure gauges are very accurate. Might be tuff to install on top of the tank if you have limited access. But, they dont neccessarily have to be installed in the tank. Anywhere you can get to the bottom (drain plug maybe) to put the pressure line will work. A gauge and small air pump to purge the line and "walla" you have a tank level gauge. You just need to know how tall the tank is and convert the static head to percentage or gallons. Simple and works everytime. I think Tank Tender sells the complete setup, or you can do it yourself.

 

[MurrayM]

I'm new at this, so take the following with a grain of salt.

(We have sight gauges, but fuel docks are far apart here, the remote ones often run out of fuel, and inlets can be very long and infrequently visited.)

I kept track of fuel added over seven months, and hours on the engine. With those known variables, and the total volume in the tanks, gives me a pretty good indication of fuel useage over time.

The PO added a 40 gallon tank, so that gives us 140 gallons in three tanks. We burned on average 1.5 gallons per hour over those seven months.

140 (gallons) divided by 1.5 (gallons per hour) = 93 (total hours running time).

93 (hours) minus 1/3 (reserve in tanks) = 60 (hours running time).

60 (hours) x 6 (consevative knots estimate) = 360 miles.

Ballpark figures for sure, subject to refinement with more experience!

 

[jleonard]

We all know how inaccurate fuel gauges are on boats.

My fuel gage is extremely accurate. So were the gages on my previous boat.

 

[Xsbank]

You do have a fuel shutoff on the tank? Close it, take off the fuel hose and attach a tee, put a valve on the vertical outlet, reattach the fuel line, add a clear hose et voila, sight gauge. Doesn't have to be "on" the tank and should be shut off unless you are looking at it. The other end goes back to the tank or tee it to your overboard vent.

My sight tube is mounted next to the trim around the door to the engine room which is very convenient to monitor, but the valve isn't. I only need to monitor one of the two tanks.

 

[CaptTom]

My tanks both have too much turn in filler hose from deck mount to tank... so that even a 3/8" dowel can't enter. NOW, thanks to your post, I'm gonna try rigging a fabric tape with svelt and non edged (so it can'y get hung up inside on anything in tank) plumb bob weight-end and try my luck!:

I had the same thing. PO used a length of regular 12-2 house wire. Just flexible enough to get around the bends, but still stiff.

I found a better way. Still in the electrical department at Home Depot, a steel "fish" tape used for fishing wires through walls.

Cost around 10 bucks. I scuffed it up with a wire brush so the fuel would stick better, and notched it every inch from the bottom. Not perfect, but it's the best solution I've found yet. I plan to order a couple of floscans when a few other budget items are behind me.

 

[Art]

I had the same thing. PO used a length of regular 12-2 house wire. Just flexible enough to get around the bends, but still stiff.

I found a better way. Still in the electrical department at Home Depot, a steel "fish" tape used for fishing wires through walls.

Cost around 10 bucks. I scuffed it up with a wire brush so the fuel would stick better, and notched it every inch from the bottom. Not perfect, but it's the best solution I've found yet. I plan to order a couple of floscans when a few other budget items are behind me.

TY CaptTom! I'll look at that. Figure I can take length of stainless wire, rough it up for depth of tank, spray paint flat black with white paint stripes at 1/8 intervals to full... and give her a try! Be easy to store as straight rod next to bridge seats; weathering would me no prob!. I'll post once accomplished. By george - This should work!

Happy Boating Daze - Art

PS: I have Flow Scan for duals... waiting for me to install - maybe this spring/summer... I'm in no rush!

 

[Captain K]

FYI--About 100 years ago I worked as captain of the last WW II era built PT boat still in service. PT 728 did history tours with paying passengers out of Key West. Her two main fuel tanks were mounted just forward of the engine room bulkhead and on either side of the vessel. The filler pipes made 90-degree bends between the deck plates and the top of the tanks. Even so, our technique was to jiggle an ordinary metal tape measure down through the filler pipes until it contacted the bottom of the tank. We had a table which gave us fuel remaining based on the number of inches of the tape that were wet by fuel. Foolproof, but oftentimes quite frustrating to get that tape to negotiate the 90-degree bends. The other captain of the boat had the magic touch, and could get an accurate reading first try. I was not so lucky, but eventually developed a workable technique. Good luck!

 

[SCOTTEDAVIS]

My fuel gauge.

100 percent accurate, 1 inch is 4 gallons, 18 inches is full. Each tank is the same (3 tanks)

I have two back-ups and a folding one for when I feel exotic and fancy. I am such a high roller.

 

[SaltyDog]

@SCOTTEDAVIS a 1/4" dowel rod wastes less fuel. Not as accurate though. The multiple use of things on board factor is way up.

 

[SCOTTEDAVIS]

@SCOTTEDAVIS a 1/4" dowel rod wastes less fuel. Not as accurate though. The multiple use of things on board factor is way up.

 

[AKDoug]

FloScan was the right answer. The unit has a reset able totalizer that will count your fuel consumption from the time it was last reset. If you know how much you started with, you will always know how much is left. I used this method for many years as a backup to my fuel gauge. Fill it up, reset the totalizer count to zero, and add up the gallons until they match what you can hold, and you are now out of fuel!

 

[Art]

FloScan was the right answer. The unit has a reset able totalizer that will count your fuel consumption from the time it was last reset. If you know how much you started with, you will always know how much is left. I used this method for many years as a backup to my fuel gauge. Fill it up, reset the totalizer count to zero, and add up the gallons until they match what you can hold, and you are now out of fuel!

I have elect dash gauges that seem pretty close to correct... but, I never really trust that type of reader... had big problem years ago due to misread from one of those.

I do keep calcs on fuel burn... to hrs... to last fill up; for knowing when to fill up again.

Also look forward to installing twin screw FloScan when I find time.

But... I really want to develop a good way to accomplish "straight stick" fuel level tests through my off center filler hose. Such as I mention on post # 15... That way of reading always tells the truth!

 

[rwidman]

You do have a fuel shutoff on the tank? Close it, take off the fuel hose and attach a tee, put a valve on the vertical outlet, reattach the fuel line, add a clear hose et voila, sight gauge. Doesn't have to be "on" the tank and should be shut off unless you are looking at it. The other end goes back to the tank or tee it to your overboard vent.

My sight tube is mounted next to the trim around the door to the engine room which is very convenient to monitor, but the valve isn't. I only need to monitor one of the two tanks.

That will work but you need to be able to operate the valve because it should be closed except when you are taking a reading (for safety reasons).

I am considering doing just that but the location of the tubes and valves is what's holding me back. They would not be convenient to get to.

 

[Art]

Note on a perfectly accurate and completely "flexible" straight-stick fuel tank reading device; thought I’d share:

I recently put together a brown color 3/16" piece of brown tweed covered nylon filament line onto one end a long thin double ended torpedo shaped fishing weight (5 oz +/-). The 2" overlap on the line at eye end of weight is stitched tightly together with thin stainless wire and then tightly double wrapped with high quality electrical tape. That’s so there is nothing inside the tank that may catch on any protrusion of the line to sinker area.

As both of my 100 gallon tanks’ filler necks have a pronounced kink in the tube to tank entry there was no way I could get even a 1/4" piece of dowel to go through.

Now by gently dropping the weight with flexible line into either tank I can tell immediately when the lower end of weight hits tank bottom... I can even clearly hear it out filler tube opening.

As the tweed cover is brown and somewhat absorptive it is easy to see by the wet/dry line the inches of fuel in the tank.

Seeing that our tanks both calc out at 4 gallons per inch (staying relatively conservative) the math is simple.

Starboard was 13” for 52 gallons and port was 18” for 72 gallons. That figures correctly as gen set feeds off starboard only.

This makes me feel very secure that no matter if my tank gauges are reading correctly or not... I now always have a conclusive tank level test method that is 100% correct!!

psneeld post # 6... about his USCG cutter days... is what lead me to this desired result... Thanks, Boat Buddy!

Happy Fuel Calc Daze! - Art

 

[psneeld]

Note on a perfectly accurate and completely "flexible" straight-stick fuel tank reading device; thought I’d share:

..................................

psneeld post # 6... about his USCG cutter days... is what lead me to this desired result... Thanks, Boat Buddy!

Happy Fuel Calc Daze! - Art

Knowing is always more comforting than believing.......have fun!!

 

[HopCar]

I rely on my Floscan. It keeps accurate track of fuel used and if it tells me I've used 48 gallons, the tank will take within a gallon of 48 gallons when I fill it.

This is the type of tape that psneeld was talking about. Note that it has a ground clip to dissipate static electricity.

The Official Site of Lufkin Brand Measuring Products

 

[Art]

I rely on my Floscan. It keeps accurate track of fuel used and if it tells me I've used 48 gallons, the tank will take within a gallon of 48 gallons when I fill it.

This is the type of tape that psneeld was talking about. Note that it has a ground clip to dissipate static electricity.

The Official Site of Lufkin Brand Measuring Products

Thanks for product suggestion!

I've got a full set up of FloScan in its original package box for twin screws; had it stored for about a year in forward cabin cabinet. Just ain't took da time ta hook er up yet! - LOL

I don't believe FS will read the additional starboard tank fuel drain due to gen set??

Till I hook FS up I’m pleased to utilize the sinker/nylon line method for accurate fuel reading.

Now that I think of it... is there any possible way for a static electricity spark off/from the line or sinker as it lowers through gas fumes into the gasoline inside tank. I doubt it seeing as no static spark from wood stick for tank level reading. I’m going net searching on this topic and appreciate any input from TF members. One spark can mean curtains for us aboard. Hummm... must locate conclusive answer on this... before using sinker/line gasoline tank-level reading method again!

Since the above Post: After my first web-net exploration regarding static electricity mentioned above... It appears that as long as the nylon line was dampened first with water that there would be no chance for static build up between gas tank and the nylon line. Therefore, it appears that the sinker and line could be dunked into water prior to tank reading. Then, after a few seconds of evaporation off the line the wet level leaved by gas in tank would still be visible for reading purposes. I will continue research!

 

[psneeld]

If the line is fed over the edge of the fuel fill...and the fuel fill is properly grounded...there should be no chance of static either...but like all things...that's assuming that your system is OK.

 

[FF]

Speaking of fuel fills , how many folks have checked to see there is a ground strap between the fill deck fitting and the tank?

A rubber hose will not serve as a ground , usually a flat tinned braided wire is frequenrly used.

Looking for the ground is one way to check the qualifications of the boat assembler.

 

[Sailor of Fortune]

That tool is called an Ullage tape. Used to sound tanks of various sizes and shapes. Typically boats and ships will have Ullage tables for each tank, that shows what each inch of fuel is.
If you sprinkle "commet" on it, the wet area shows up much better. You need to have a general idea of fuel level. Some of these tanks are 20' plus deep.
Water paste can be added to the plumb bob for detection.

 

[Wil]

That tool is called an Ullage tape. Used to sound tanks of various sizes and shapes. Typically boats and ships will have Ullage tables for each tank, that shows what each inch of fuel is.
If you sprinkle "commet" on it, the wet area shows up much better. You need to have a general idea of fuel level. Some of these tanks are 20' plus deep.
Water paste can be added to the plumb bob for detection.

Sorry for the ignorance, where do you get 'commet'? Kept getting 'comment' and 'comet' in searches.....