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Old 05 August 2011, 11:48   #1
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Oscillating fuel meter ribcraft

Hey ,

I have ribcraft 5m with an underdeck fuel tank of 55 liters, but when I am at the sea the pointer oscillates from empty to full and back to empty. And the first and last 15 liter are not visible, so my opinion is it is quit inefficient and rubbish. A fuel meter must work 100% correct because it is not acceptable during long trips that the final liters you still have are not shown on my analog meter.


If you have some suggestions to help me with this problem it would be very helpful.
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Old 05 August 2011, 12:10   #2
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It is usually a float that moves up and down inside the tank. It is easy to see how on a bouncy boat, and depending on the position of the sensor and trim angle that gauges can be inaccurate. A gauge which says you are "empty" when you still have 15L left is far better than one which says you have 15L left when there is none.

There might be better gauges but they will NEVER be 100% accurate. Most people manage fine without that level of accuracy. Passage plan should ensure you have plenty of fuel before you leave, and dip the tanks (someone on here uses a broom handle with graduations marked on it) for accurate levels when you start (and e.g. before setting off after lunch).

An alternative (but expensive?) approach is to measure the amount of fuel you are actually consuming (which by knowing the tank volume and when it is refilled can tell you how much is left) - I think Floscan is one of the more common makes. But it also will not be 100%.
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Old 05 August 2011, 14:32   #3
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Quote:
Originally Posted by AVRibber View Post
Hey ,

I have ribcraft 5m with an underdeck fuel tank of 55 liters, but when I am at the sea the pointer oscillates from empty to full and back to empty. And the first and last 15 liter are not visible, so my opinion is it is quit inefficient and rubbish. A fuel meter must work 100% correct because it is not acceptable during long trips that the final liters you still have are not shown on my analog meter.


If you have some suggestions to help me with this problem it would be very helpful.
Yup, they all do that, not a lot you can do about it with an analogue gauge/sender. What engine do you have?
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Old 05 August 2011, 14:40   #4
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I have a Yamaha 60 HP , normally yamaha has a connection to connect the speedmeter ( where also battery en km is mentionned) to the fuel tank. But the factory who produced that part in Italy is bankrupt , and those pieces or not availible any more.

Someone heard of the Navman fuel meter or fuel flow meter ?
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Old 05 August 2011, 16:35   #5
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When taking over my Ribcraft I was advised the fuel guage was notoriously inaccurrate. Mine reads full until about half empty, then comes off full. I startto get concerned when it shows half!

I estimate how much I use based on mileage and speed, and when I top the tank up it's been pretty accurate. I'm averaging 0.85l/nm.

I'd estimated my use each trip then topt he tank every so often to validate the estimate.

Still a great boat though!
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Old 05 August 2011, 16:48   #6
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Unfortunately stand alone flow meters are hard to source. I use mine( newly sourced from RIBnet ) to learn the most economical speed for each condition. In mine set-up, as a small surprise, seams like decreasing the speed will not increase economy( litres/nm), roundabout 28 knots is better than any speed less than that. And again at WOT, mileage is almost the same(light load)...

But for checking the range, i don't use any meter, always fill the main tank(70 L) before any longer trip, that will give about 70+ nm range. Then i have one or two 20L cans as reserve pending on load/conditions. I guess a WEMA ( looks ok) would be attachable to Yamaha multi gauge, but haven come that far yet.
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Old 05 August 2011, 19:53   #7
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I have got a 2001 Ribcraft 585 with a similair tank and my fuel guage is very good.

I would check all of the wiring for corrosion first as this can give funny results.

It may be a good idea to take out the sender unit and measure the resistance and you move the doughnut shaped float up and down. This will confirm whether this unit is ok the Ohmns

Disconnect the sender from the gauge. Attach a VOM, the positive (red) lead to the sender’s output post and the ground (black) lead to the sender’s flange on the tank. Most marine fuel senders have a resistance of 33ohms to 240ohms. Using the gauge as your guide, the VOM reading on the resistance scale should indicate 33ohms with a full tank, 240ohms at empty and somewhere between 80ohms to 120ohms when half full. A more accurate test is to unscrew the sender from the tank, attach it to a VOM (as above), and manipulate the float, moving it to the full (up) and empty (down) position while noting the resistance on the VOM. If the sender checks out, the gauge may be at fault. But before removing, obtain another sender that you know works and connect it to the gauge.
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Old 06 August 2011, 17:07   #8
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Hi,
i've had the same problem with my 4.8 Ribcraft and solved it by using the navman 2100
gauge.
Unfortunatly Navman stopped the production for that useful item keeping in mind that most fuel mesuring systems are integrated into today's advanced navigation instruments.

To solve the problem it's possible to buy a Lowrance navigation system with an supplementary fuel mesuring instrument into the fuel line,

or

the new Lowrance multimesuring gauge ( forgot the name, simply look onto the Lowrance site) but it's, like most new stuff, more expensive than the old navman( or Northstar, the same).

Cheers
Eric
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Old 06 August 2011, 17:27   #9
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The fluctuations are due to under damping, either at the sender or the gauge end. The missing top and bottom range is because of incompatibility of the 2 units range. I'd make a very wild guess that it's not the right gauge, possibly even been that way since manufacture.

What type of gauge is it? Have you had the sender out, was the float visible on a central pole?

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Old 06 August 2011, 23:57   #10
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Talk to Ribcraft
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