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Old 05 August 2011, 10:48   #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, 11:10   #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, 13:32   #3
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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, 13:40   #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, 15:35   #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, 15:48   #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, 18:53   #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 senderís output post and the ground (black) lead to the senderís 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, 16:07   #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, 16:27   #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, 22:57   #10
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Talk to Ribcraft
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Old 07 August 2011, 03:02   #11
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I've already had contact with ribcraft and they said they couldn't do something about it.

The Navman 2100 , have they stopped production of it ? because I could still find it on there website .
And in the specification is mentionned the engine must be between the 90 an 300hp , but I've 60HP. ( but I think to switch over to a 90HP so in the future this won't be a problem.

The lowrance instruments looks nices , but a bit expencive I think.
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Old 07 August 2011, 05:19   #12
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( but I think to switch over to a 90HP so in the future this won't be a problem.

The lowrance instruments looks nices , but a bit expencive I think.
Buy an Etec & problem solved, that's why I asked you which engine you had earlier. In-line fuel flow sensors are notoriously unreliable & inaccurate. An engine with built in fuel management in the EMM is the way to go
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Old 07 August 2011, 05:51   #13
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Thanks for your suggestion, but I prefer a Yamaha engine. I am very very satisfied of my Yamaha , and if there would be a problem with my engine, the locations where I sail have the spare parts within max 24 hour. My friend has an Etec , he needs to wait about minimum of 6 weeks to have his spare parts. So no Etec sorry.
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Old 07 August 2011, 06:06   #14
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You don't need Etec to get engine based fuel consumption data. Yamaha command link can provide this - if the engine is putting out the data: Yamaha Command Link

I think the F60 can provide this - although you obviously want to check with Yammy that your specific model/year gives the data you need. If you have a modern fancy plotter you might even be able to get this data on the plotter without buying new gauges (I think CommandLink is NMEA2000 compatible?). Of course if you have an old 2 stroke 60 HP then this is probably all irrelevant.
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Old 07 August 2011, 06:26   #15
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Okť , thanks. But it is not an old 2stroke yamaha , it is an F60 CETL from 2005, 4 stroke.

I have the "ROUND COMBINATION SPEEDOMETER AND FUEL MANAGEMENT GAUGE" but the connections to the tank belonging to me F60 are no longer availible. I already checked that.
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Old 07 August 2011, 06:50   #16
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someone on here uses a broom handle with graduations marked on it
that'll be me then. B*****d to dip at 30 knots
Underfloor tanks by definition have to be shallow boxes so a small drop in height which the guage is reading is a big drop in volume. Any guage is gonna struggle with that. They are usually not "dippable". Fuel moves around fore to aft moving the C of G of the boat. Thats why I dont like'em-but they are often a neccessary evil. Our built-in tank is above deck in the front consol, I can dip it so I know what fuel I have at any time, its relatively easy to get at and any leaks can be seen/smelled immediatly. It is however far easier to fill a portable tank unless you have waterside fuelling which we dont have for petrol so we tend to run as much as possible on the portable aux tank, the boat having a changeover valve for fuel source.
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Old 07 August 2011, 12:22   #17
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Buy an Etec & problem solved, that's why I asked you which engine you had earlier. In-line fuel flow sensors are notoriously unreliable & inaccurate. An engine with built in fuel management in the EMM is the way to go
Same as that!! A tad exspensive though,always better to over compensate with fuel either way.
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Old 07 August 2011, 15:52   #18
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Hmm, before forking out on an Etec think about the last time you went out in your car. Did the gauge swing wildly when you went over a bump? Did it fall when you went round a roundabout? Did it stop reading when you filled the tank to the neck, or drained it dry? If the answer to all the above questions is no, then I'd be back on the phone to Ribcraft.

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Old 07 August 2011, 18:04   #19
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Okť , thanks. But it is not an old 2stroke yamaha , it is an F60 CETL from 2005, 4 stroke.

I have the "ROUND COMBINATION SPEEDOMETER AND FUEL MANAGEMENT GAUGE" but the connections to the tank belonging to me F60 are no longer availible. I already checked that.
I might be wrong but does the CommandLink not measure the "fuel flow rate" from the engine? The manual isn't specific but I can't imagine any fuel tank level sensor being accurate enough to measure instantaneous fuel consumption. The fuel level part is only going to read similar to your current display although it may have better electronic damping.

If this is the case then the amount remaining is simply the tank volume less the amount consumed, as I think someone else suggested.

I'm surprised that the cable / part you need is no longer available as it looks like it is standard across the range so loads of people must need them (unless I have misunderstood which bit is not available 6Y8-8356N-0 ?)

Quote:
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Hmm, before forking out on an Etec think about the last time you went out in your car. Did the gauge swing wildly when you went over a bump? Did it fall when you went round a roundabout? Did it stop reading when you filled the tank to the neck, or drained it dry? If the answer to all the above questions is no, then I'd be back on the phone to Ribcraft.
most cars probably have 10L left in the tank when they read zero. Many cars seem to sit at "full" for a long time before the gauge starts to move - exactly the issue described here (although maybe slightly worse). Before cars had "computers" controlling the dashboard I regularly noticed my fuel level change going up and down hill. And this is in a baffled tank, produced in high volume with a "matched" level sensor.

I guess you might be able to get a sensor which fits the size of tank better, or reposition it so it is less sensitive to the fluctuations in the tank, but it is a boat tank sensor and measuring liquid level on something bouncing about is never going to be perfect. Are Ribcraft really going to be able to eliminate the problem from hundreds of miles away?
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Old 08 August 2011, 05:24   #20
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Both my Ribcrafts have suffered the same problem as did the Osprey before that. The fuel gauge is ok when the boat is at rest in calm water or on the trailer on level ground. After that it's useless & I doubt that any number of calls to Ribcraft will resolve it. I suggested etec because I know that they have fuel management capabilities built in which are very accurate (to the litre) I'm sure other manufacturers have the same capabilities.
As for comparing vehicle fuel gauges to boats, apples & oranges! Even the most extreme 4x4 doesn't encounter the rapid changes in attitude & G forces that a gentle ride out in a RIB produces. TBH if you rely on ANY kind of fuel gauge as your only means of calculating your remaining fuel, you'll eventually find yourself stranded one day, what happened to passage planning?

ee lad, tha can't educate pork
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