Fuel tank gauge

donm

donm

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I thought I would take the fuel tank out this winter and clean it. It is an odd shape being in the depths of the bilge and I have to take up the cabin sole to dip it but because of its shape it is not half full when it shows halfway on the dipstick. So when I have it out I will accurately calculate the capacity and the various quarter, half and three quarter levels, but has anyone fitted a level sensor/gauge that I could easily fit whilst it is out?
 
Yep ... about £30 from eBay (seller id : internationalmarinesupplies ... a mechanical float device on a lever that actuates a rheostat ... a 12v source is applied to the mechanism and the rheostat alters the voltage to a meter sited in my cockpit. It's basically same as older style car gauges. In fact if you can get hold of a Land-Rover gauge set-up - its same ..........

Simple to fit ... comes with measurement figures to adjust length of float arm and vertical leg to suit tank.

I also measured my tank and calculated a graph of contents - so that I can still dip with my stick and compare to the gauge. Especially as you do not have square / uniform tank - same problem for me !!

So far well pleased ... as with all gauges you need to watch and get comfortable with readings.
 
I have a tank in my yard full of red diesel and I need to know how much was in it, I looked at gauges then my father told me an idea they used years ago when he flew planes for the RAF.

Its simple to fit but you need to see the tank to see the fuel level. All bits can be bought local.

You drill 2 holes under each other, one as high as you can, the other as low as you can, both holes put in a threaded outlet like you have as a drain plug on the back of the boat and screw in 2 right angle joints bought from plumb shop attatch a straight clear hose to both ends so it runs from down next to the tank. As you fill up the fuel it will fill the hose and you can see how much fuel you have.

Its simple and cheap.
 
You only need one hole and some clear pipe. I think your insurers might be happier if it had a self closing valve (see asap web site) at the bottom!
 
Im sure for safety there needs to be some tweeking thats just the basic idea.

Not tried it with one as you would need to allow air to escape and the hole at the top allows this inside the tank.
 
I'd suggest the simple solution is to start with an empty tank and a blank metal dipstick.
put a measure of fuel in the tank, dip it, and mark the dipstick "n gallons"
Another measure - another dip - another mark on the stick "2n gallons" etc.
Even sight glasses can block up but you can't go wrong with a dipstick. (Cue for a quip!)
 
the sight tube is an old and trusted way to do it ... but the oroiginal post mentions that he has to lift sole to get to tank ... so the tube idea is not going to work !

Tip for the tube ........... with red diesel it's easy to see the level. If you use ULSD road diesel will not show so well - so take a length of card and paint diagonal barber poles lines on it ... thick lines ... Fix behind the tube.
Now the level is easy to see as the fuel will cause distortion of the line as viewed through tube ... refraction.
 
tanks vented already. the top tube can be left to vent to atmos as long its above the tank top, i used this and teed inti the vent overboard, simple, if you dont want to drill a hole you can tee into the fuel line and the vent when the fuel valve is open it gives a reading fuel (if the tank is a bottom gravity fed system - woever ensure the tube has an isolation valve in case of leaks and to prevent the engine sucking air if the fuel vv is closed whilst underway!
 
there are other gauges of same style on ebay ... so have a look through - you may be lucky to find cheaper !

When I fitted mine - I managed to alter the old gauge plate to take the new one ... I also thought carefully about the motion of the boat and "slop" of fuel ... before deciding which direction the float arm should point !! Thinking that maybe I could reduce the effects of heel etc. when sailing on gauge indications ... don't bother !! fit best you can !!
 
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Thanks for the suggestion but as the tank is beneath the cabin sole an external sight tube will not work on this occasion

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Does the cabin sole sit on the tank or is there a gap ? Just wondered if a variant of the fuel gauge on my generator may be of use ... it's a short arm float that swings a pointer along a scale under a glass window. No electrics .... just pure pivoted float arm / pointer. OK it's not great scale but gives a reasonable indication. If the sole is sitting on the tank ... maybe this could be fitted with a cut-out in sole to view ?
 
I was only suggesting it ... but don't know where you would get one from.

I've seen them on plastic outboard remote tanks ... my Generator tank ... etc.

It's a clear plastic round window ... under it is a metal plate with a slot running across its diameter. The plate either side of the slot is painted red ... yellow and finally green as it gose across the window. There is a black plastic arm that has a cross piece and this pivots to a float arm in the tank. As the float arm moves in the tank with the level - the cross piece moves along the slot to show how much fuel in the tank. Simple, crude, no scale to it ... but effective.

The best I reckon is the 12v gauge / arm job I first mentioned ... it works !! gauge even has a light !

I wired mine up so that it only powers when engine switch is on - saving power from my meagre batterys !. (I have a flick switch that disengages ignition low power circuit stopping solenoid from being activated, same switch also cuts energiser to alternator ... plus now cuts power to gauge when engine off. I did this because I don't have an ignition key and panel ... the old system fitted by previous had separate switches for all ... so I of course forgot alternator one time ..... ).
 
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Have a look at bes here

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Fantastic ... but his tank is below cabin sole ... /forums/images/graemlins/wink.gif

Would be good for my tank which is under fwd bunk and therefore above bilges ... but then again - a few plumbing fittings ... a clear plastic tube and bingo .....
 
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If you look a bit further down the page you will see a dial type float gauge plus an electrical one

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If by electrical you mean the watchman system this requires mains power at the receiving end. We have this on our central heating oil tank and it is excellent, but not sure whether it would be any use on a yacht even if you have AC power via an inverter?
 
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