Ultrasonic Tank Level Gauges?

[Wee Venture]

This question relates to an active thread on “fuel level” but is different enough from the OP’s question that I decided to post it separately as a new thread. Has anyone had experience with the Maretron ultrasonic tank level sensors? I have seen a number of references on Tugnuts and elsewhere to the significant inaccuracy of the original equipment mechanical fuel level sending units (and water tank level gauges also, for that matter). Neither the fuel tank gauge nor the water tank gauge reads accurately on our R-31. This is not unique to Ranger; we previously owned a different model boat where the fuel gauge was “reliably unreliable.”

On paper the Maretron unit (TLM100-01 for diesel or water) looks like a great solution. It’s a bit spendy at a little under $200, but if it keeps you from running out of fuel just once, it’s worth it. It supposedly mounts in the same place with the same gasket and hole pattern as the OEM mechanical unit, and interfaces with the NMEA 2000 network. Does this mean it can be read directly on the Garmin display?

The existing mechanical rheostat units have been around for decades and are prone to failure. But new technology is not always better. So has anyone installed these units (or any other replacement gauges)? Are they accurate and reliable? I would be interested to hear your experience.

John B

 

[knotflying]

According to the directions the tank bottom needs to be flat and smooth. One should determine the tank configuration at the point of installation. The other issue as with the standard gauge is pitch. When the bow is up you won't get a true reading. As far as the Garmin being able to accept the device, you may want to contact Garmin. For my money I would rely on the Garmin "fuel remaining) and make sure I am diligent when filling.

 

[Wee Venture]

Knotflying, thanks for the response. I understand that running in a bow-up attitude would skew the reading (true for mechanical gauges as well) and I would be willing to stop or slow to idle when taking a reading. I do rely on the Garmin “fuel remaining” and have found it to be highly accurate, but I tend to subscribe to the “redundancy” philosophy and like to have backup systems in place (spare parts, redundant electronics, etc.). We like to cruise in more remote areas - we spent six weeks in the Broughtons this last summer and plan to go to Alaska next. It would be reassuring to have a second source of data for something as important as fuel. At this point, our original equipment mechanical fuel gauge does not give me much security if the fuel flow link from the engine starts becoming inaccurate or I accidentally lose track of how much fuel I added. If the chartplotter itself goes down, I have an iPad loaded with Navionics for navigation but the fuel data is stored locally on the Garmin unit and would be lost.

 

[Larry H]

I am also concerned about fuel remaining. I keep a simple log of the daily runs and at the end of each day's run, I look up the miles traveled, engine hours and fuel remaining. I write those down on the log. If the Garmin won't start up one day, I have that information on paper. I too have an iPad with Navionics as a back up nav unit.

 

[ixlr8]

I am also interested in a more accurate tank level gauge. Especially since last time I took my boat in for warranty service, the fuel remaining in the Garmin and the Yamaha gauges were both reset to 0 and the dealer seems to have no idea how it happened.

 

[BB marine]

viewtopic.php?f=18&t=10780
I posted this last winter after finding the fuel gauge useless. I spoke with a Volvo technician about the inaccuracy of the gauge. He said if the factory properly calibrated the sending unit it’s accurate. I recalibrated it and find it to be within 2 gallons of the Garmin. The boat must be at a idle position to get a accurate reading. I was told
That Volvo stresses the importance of accurate calibration to the manufacturer. Fluid motion uses the full tank calibration. This is not an accurate calibration. Most do not see the importance of the gauge. I like having a few different checks to confirm accuracy. I have that now.

 

[knotflying]

As a former pilot the best accuracy was knowing your fuel burns at various RPM's and keep track and log it. Yes that means some work while cruising along, but what else do you have to do? Making it a habit of noting fuel remaining on the Garmin is a good habit as well. Relying of a fuel gauge is probably the least reliable. As they say, "They are accurate when full or empty."

 

[BB marine]

I agree 100% Mike. Knowing your fuel consumptions and fuel ranges at different cruising speeds and engine RPM is very important. Strictly relying on a gauge or a devise to calculate fuel on board is not always completely accurate. I rely on my personal calculations, Garmin, and fuel gauge. Before I calibrated the fuel gage I relied on My calculations and Garmin. The Garmin was always off by approx 5%, not bad. The fuel gauge was off by at best 20% mostly higher then that. My calculations were very close to the Garmin but the information that I am using is the information from the engine fuel management which is read by the Garmin. The sending units now are more accurate then old fuel tank units. The new senders need calibration to be accurate. When I get in my car or truck and drive some where I look at the fuel gauge and know that I have enough gas or fuel to get to where I am going. I rely on the fuel gauge and it is for the most part accurate. I know operating a boat or a plane is different. There are not fuel stations on every corner. Having a fuel gauge as accurate as possible is important. Calculating fuel range is important. Using the information from the engine management system and reading it through the electronics is important. The more accurate information the better when cruising with limited fuel stops. If I have a gauge on board I want it as accurate as possible, its just another resource for comparison for accuracy. Hell we are lucky to have all this electronics. My dad measured his boats fuel consumption with a hour meter and a wooded stick. I don't ever remember him running out of fuel.

 

[knotflying]

Before I got in my plane I dipped the tank with a hollow tube that had gradations on it. I always new what I had when I started and what I needed to get where I had to go.

 

[BB marine]

While I agree with Mike. I also feel that all efforts to Calibration should be done for the ( stereo type) hop in the boat and go look at the gauge and know there is fuel. With a little effort it can done calibration sender and Volvo gauge. Here are yesterdays comparisons while pulling into the marina. With Garmin and Volvo gage (calibrated sender)


The Sender is reading .8 gallons off of the Garmin. My calculation was 2 gallons off of both of these readings, We took on board 27 gallons of fuel in our 80 gallon tank that usually doesn't fill to 80 gallons. All close enough for me.