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Author Topic:   NAVMAN 3100 Fuel Instrument
jimh posted 07-07-2005 08:31 AM ET (US)   Profile for jimh   Send Email to jimh  
I just returned from a five day cruise using a Navman 3100 Fuel Instrument to monitor my fuel consumption. This device is even cooler than I thought.

The principal attraction of the NAVMAN 3100 is its ability to accept a SPEED input, either from a Navman paddlewheel sensor or from a NMEA connection (such as from a GPS receiver). With a speed input, the device will compute instantaneous fuel consumption rates in MILES PER GALLON (or other units).

The device also tracks the amount of fuel used. It provides a continuous tank level indication (a thermometer-style vertical bar graph). You can also select display of gallons remaining in the tank. Total fuel use is also recorded and displayed.

In addition, the device also tracks engine hours. It also displays battery voltage.

I was very pleased with the device. Once I became acquainted with the controls and menus, it was very simple to operate the device and to select the information I wanted to display. The size of the display and the front panel buttons are appropriate. It is easy to see, and the buttons are large enough and far enough apart that operating them is easy even in a small boat underway at speed.

When I purchased the Navman 3100 I did so in preference to two other choices:

--Navman 2100
--Navman SONAR or GPS with fuel transducer option

The principal difference between the NAVMAN 2100 and NAVMAN 3100 models is the ability to accept a SPEED input and compute fuel economy. I found this very useful.

The principal difference between the 3100 and a SONAR or GPS with the fuel transducer option is the separate display device. I found this preferable to switching the display on the SONAR to another page.

Having more accurate information about fuel usage, particularly gallons remaining in the tank, was a pleasant addition to our small boat cruising.

Peter posted 07-07-2005 09:06 AM ET (US)     Profile for Peter  Send Email to Peter     
I probably look at the display on my Navman 3100 more than any other gauge. The nice thing about the instant MPG readout is that it helps confirm to me when my engines are truly in sync as the MPG typically increases by 5 to 10 percent when they are versus when they are not. The instant MPG readout of the Navman 3100 also helped me figure out which set of propellers of the 5 sets I've tried were best for my boat.

The gallons remaining in tank is a very useful feature for me as well. I have three tanks, one main and two saddle. They are used as if there are only two tanks -- although both motors can draw from any tank at any time, I have them either draw fuel individually from one of the two saddle tanks or they both draw from the main tank. I usually draw from the saddles first and then the main. The bar graph coupled with the numeric remaining in tank helps me determine more precisely when to switch from the saddle tanks to the main tank.

It certainly is one of the better additions I have made to my boat.

alfa posted 07-07-2005 02:44 PM ET (US)     Profile for alfa  Send Email to alfa     

did you calibrate the fuel sensor as advised in the Op Manual ?

Alain 22' Outrage

jimh posted 07-08-2005 07:17 AM ET (US)     Profile for jimh  Send Email to jimh     
I have not altered the calibration of the fuel flow transducer from the factory setting.

In order to adjust the calibration from the factory setting it is necessary to have an alternative method of measuring fuel flow with a degree of accuracy which is believed to be greater than the the existing calibration. At the moment I do not have such an alternative method available which I believe would be more accurate than the existing.

The simplest approach to measuring fuel flow would be to defer to the calibration of the fuel flow transducer on another pump, for example, on the pump dispensing gasoline at the point of sale.

One would fill the vessel's fuel tank to a particular level, run the engine for sufficient time to consume a reasonable quantity of fuel, perhaps 5 gallons, then refill the tank to the initial level. Measurement of fuel flow would then be deduced by comparing the indicated amount of fuel used on both gauges, relying on the fuel flow transducer in the gas pump dispensing the fuel as the standard.

The accuracy would be limited by:

--the precision to which the tank was re-filled to the same level
--the precision of the fuel flow transducer on the dispensing pump

The fuel system on my boat does not have provisions for connecting an alternative tank, so the main 77-gallon tank would have to be used. I do not believe that I can re-fill the 77-gallon tank to the same level with a great deal of accuracy, unless I were to fill the tank so that the fuel level rose above the tank top and into the filler hose. At that level of fill you could observe the fuel level visually and re-fill to the same level.

I am reluctant to fill the main tank above the top of the tank for many reasons, including to avoid having fuel sit in the filler hose which is composed of 13-year-old rubber for long periods of time.

In order to minimize small errors in measurement in the refilling of the tank to the same level in the calibration process, the more fuel used in the calibration run the better.

After measuring the flow of over 200 gallons of fuel, it appears to me the factory setting is accurate enough for my purposes at the moment. If there were an error of 10-percent, I would have seen a variance of 20-gallons at this point, but I do not see any difference between apparent consumption and measured consumption of that magnitude. If there is an error, it appears to tend to slightly overstate fuel flow rate. An error in that direction is preferable to an error which understated fuel flow rate. (That could lead to running out of gas.)

DaveH posted 07-08-2005 08:20 AM ET (US)     Profile for DaveH  Send Email to DaveH     

Try using a small 6-gallon portable for calibration. You can fill very accurately and not worry about the variances you decribed.

DaveH posted 07-08-2005 08:24 AM ET (US)     Profile for DaveH  Send Email to DaveH     
Sorry Jim, I just noticed your set up not allowing the auxillary tank. Please disregard.
jimh posted 07-08-2005 08:43 AM ET (US)     Profile for jimh  Send Email to jimh     
Dave--I plan to change the fuel system to allow connection of an auxiliary tank. I think it will be a good addition, not only for calibration of the fuel flow transducer, but it will allow other options like:

--brewing up small batches of treated fuel for winterization or cleaning of the engine;

--carrying extra fuel in on-deck tanks on long trips.

It is on the list of projects. However, I have not seen any significant errors in the factory calibration, so there is no mandate to re-calibrate immediately.

JMARTIN posted 07-08-2005 06:24 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
Jim. I have a very similar set up to your boat with a 77 gallon tank. I have filled up 4 times at the same fuel dock, trying to pump at the same speed, and trying to fill to the same "first vent spit" level. The weight and trim on the boat has been constant. My new uncalibrated Navman 3100 has been less than one gallon off with the pump meter on each 30 to 40 gallon fill. The Navman shows 6 to 8 tenths more fuel used than the pump shows. Now the unknown is, how accurate is the pump meter. The fuel dock did have some improvements done to it this winter and the meter looks new. I assume it was calibrated before it was put into service. The legal limits here in Washington State is that a pump can be plus or minus 3 cubic centimeters of product on 5 gallons. I have been told that the State Weight & Measurement enforcers never check fuel docks because the fuel tanks are so far away from the pumps they are checking and they do not want to haul the five gallon tester cans full of product that far. John
kamie posted 07-08-2005 08:36 PM ET (US)     Profile for kamie  Send Email to kamie     
I have only filled the tank once since I got the Navman but the gallons used on the navman was pretty close to the amount the tank would take. Since I was filling at a gas station I filled until the auto shutoff kicked in. My plan is to do the same thing for a second time on Sunday and see what the readings are. Assuming it's close, I will probably not try to calibrate the Navman any more and just roll with the settings as they are.
Riverwhaler posted 07-10-2005 08:46 AM ET (US)     Profile for Riverwhaler  Send Email to Riverwhaler     
Have 3100 also and really glad I added it. I haven't calibrated it either but last week sent an email to Navman questioning the need to do it. Maybe they will tell me the the variance + or - we might see. I'll let you all know.
Riverwhaler posted 07-11-2005 12:07 PM ET (US)     Profile for Riverwhaler  Send Email to Riverwhaler     
Here is what Navman said about calibration from his email.
And I copy and paste....

The fuel 3100 is accurate to within 5% out of the box and within 1-2% after calibration. The reason for the suggestion to use a 6 gallon fuel tank is accuracy of a know amount of fuel used. You can use the fuel tank in the boat as long as you have an accurate method to measure the actual fuel used.

5% is good enough for me.

andygere posted 07-11-2005 12:55 PM ET (US)     Profile for andygere  Send Email to andygere     
I have a Standard Horizon FF41 (same as the Navman F2100), and I used the method jimh described to calibrate it. It was easy to do, and the accuracy did improve a few percent. One nice thing about having your fuel monitor measuring as accurately as possible is that when you go to fill up, you know with good precision how much gas to put in. This lets you slow the pump down in time to prevent gas from blowing out the vent. Jim makes a good point about leaving the filler hose full of fuel, but since my big carbureted Mercury is burning 2 gph even as I idle up the harbor, a few minutes of running on plane takes care of any remaining fuel in the hose.

After learning about the nice features on the 3100, I'm beginning to wish I sprang for one of those, instead of the simpler (and less expensive) FF41/F2100.

DeepSouthWhaler posted 07-11-2005 02:05 PM ET (US)     Profile for DeepSouthWhaler    
Does anyone know if the fuel flow sensor for Navman will work with older Optimax engines? I have a 1999 (pre-smartcraft) 150HP. I just ordered the Navman Tracker 5600 and I was thinking about getting the fuel sensor. I just wasn't sure if it would cause a fuel starvation problem for this engine.
JMARTIN posted 07-11-2005 02:36 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
I would not consider a 1999 model "older", since I have a 1992. I would not think you will have a fuel stravation problem because my thirsty 1992 200 hp Evenrude shows 20+ gallons an hour on the Navman and no fuel stravation at WOT. I have not stayed at WOT for longer than 30 seconds though. 20 gallons an hour is like 60 bucks an hour, ouch! John
Peter posted 07-11-2005 03:08 PM ET (US)     Profile for Peter  Send Email to Peter     
You should check with Mercury on that question. My recollection is that the Optimax's fuel pump doesn't have enough capacity to pull fuel through a boat mounted as well as the Optimax mounted fuel/water separator.
jimh posted 07-11-2005 10:59 PM ET (US)     Profile for jimh  Send Email to jimh     
Re the NAVMAN 2100--this is a cool device, too, although it lacks the instantaneous MPG computation. I think once you get acquainted with your boat and motor and become familiar with the fuel consumption rates, you may use the instrument more for monitoring overall fuel use and tank levels. In the initial period, however, it is fun to watch those MPG numbers.
andygere posted 07-12-2005 12:35 PM ET (US)     Profile for andygere  Send Email to andygere     
I usually have my FF41/F2100 displaying the burn rate in gph. I find this is really a great tool for dialing in the most efficient cruising speed for the current conditions. I do like the idea of having that information converted into mpg, because it would allow you to do trip planning easily and with confidence. For example, on a long offshore run for tuna, you could quickly determine if you have enough fuel to run another 20 miles to get to a "hot" bite, and still have enough in reserve. I'm sure this is a helpful tool for planning fuel stops on extended cruises as well. Technology is great, and it can really add to having more fun (and safety) on the water. On my first Whaler the only instrument I had was an inexpensive compass. How did I ever survive? : )
Peter posted 07-12-2005 12:54 PM ET (US)     Profile for Peter  Send Email to Peter     
Another nice thing about the 3100 is it will display range in miles to empty if you wish provided it is receiving a speed input. It's a bit amusing to see the display indicate a range of over 1,000 miles at idle speed on my boat with over 200 gallons of fuel on board but its right on the mark. My motors consume about 0.6 GPH combined at idle and the slowest speed the boat will go with both motors engaged is about 3.8 MPH.
Perry posted 12-28-2005 01:45 AM ET (US)     Profile for Perry  Send Email to Perry     
Jim, Peter, I was wondering if either of you have connected your Navman 3100 to a GPS? I tried and am not able to get them to communicate. The GPS (Garmin 60c) NMEA out wire is connected to the Navman 3100 NMEA in wire and the GPS is set to interface via NMEA in/out. The Navman is also set up for GPS speed input. Still no communication. Any ideas?

I'm still waiting for e-mail tech support from Garmin and Navman.

It's great having GPH readings but ut would be nice to also have MPG, range, etc to be functioning too.

Perry posted 12-28-2005 02:22 AM ET (US)     Profile for Perry  Send Email to Perry     
As for calibration of the unit, I burned 5 gallons from an auxillary tank and the Navman read 4.5 gallons used which I believe is 10% error. Now that I calibrated it, it should be good for 100 hours when the manual says to do it again to compensate for wear of new moving parts.
jimh posted 12-28-2005 02:30 AM ET (US)     Profile for jimh  Send Email to jimh     
Perry--Yes, my NAVMAN 3100 and my GPS have been talking since day one. I will have to look for the instruction books and see if I left myself any notes. The connection involves several layers:

First, you have to find an OUTPUT from the GPS and an INPUT on the NAVMAN. These have to be connected with due care for the polarity and grounding.

Next, you have to configure the GPS to send the right NMEA SENTENCE. This may be the sticking point. Buried in the NAVMAN technical appendix is a list of sentences which can be used. Buried somewhere in the GPS should be a menu where you can select the sentences to be transmitted.

Finally, you have to configure the NAVMAN to use the GPS input.

My recollection is that this was not quite made explicit in the instruction book. I will try to dig them up tomorrow and see if I can be of more help.

Peter posted 12-28-2005 07:29 AM ET (US)     Profile for Peter  Send Email to Peter     
Perry - My Navman 3100 is also connected to the GPS just as you describe. Assuming its connected correctly the only thing I can think of is that you don't have the GPS talking at the right baud rate. Unforutnately, my boat is put away for the winter so I can't fire up the GPS to see what that is set at. I would simply play around with the baud rate settings to see if that makes it work.

Chuck Tribolet posted 12-28-2005 07:47 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Perry: Did you configure the GPS for NMEA out? Garmins default
to a Garmin propriatary protocol on the serial (NMEA) ports.

4800 bps is the most common speed.


Perry posted 12-28-2005 02:19 PM ET (US)     Profile for Perry  Send Email to Perry     
Jim, Peter, Chuck, thanks for your replies. I finally got a response from Navman. They informed me that there is a misprint in my owner's manual. They mislabeled the NMEA in and out wires so I had it wired backwards. I noticed the manual has a 2003 date on it. They said new manuals have the misprint corrected and they don't know how I got one of the older versions of the manual. Too bad I wasted two hours of beautiful Hawaiian weather tinkering with the GPS trying to figure out why it wasn't sending info to the Navman. I will probably go out tomorrow and make sure everything works ok.

Thanks again...Perry

JMARTIN posted 12-29-2005 03:13 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
Perry, I have a Navman 3100 that is not talking to my Lowrance gps. My book is a 2004 and shows "NMEA in" is White

"NMEA out" is Yellow. What dib Navman say on colors? John

jimh posted 12-29-2005 03:46 PM ET (US)     Profile for jimh  Send Email to jimh     
Another nice feature of the NAVMAN 3100 is the collection of long term data. At the end of the 2005 boating season, my NAVMAN 3100 told me the following:

Seasonal Data 2005
Gallons used = 508.7 gallons
Total log = 941.3 miles
Total hours = 67.3 hours

From those numbers I computed
Average fuel economy = 1.85 MPG
Average speed = 14.0 MPH
Average fuel flow = 7.55 GPH

Perry posted 12-29-2005 05:20 PM ET (US)     Profile for Perry  Send Email to Perry     
John, you also appear to have a manual that has the misprint. According to the Navman technician, the yellow is NMEA "IN" and the white is NMEA "OUT". This also is the case with my GPS. The Garmin tech said the NMEA "OUT" wire is almost always white in color.

I am taking my boat out this afternoon and test to make sure everything is working.

JMARTIN posted 12-29-2005 05:53 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
Perry, Mahalo.

I would think that Navman could afford a proof reader for thier installation manual. Now, if Lowrance is correct in yellow being transmit, I will be comunicating. John

Chuck Tribolet posted 12-29-2005 06:10 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
The Garmin tech is wrong.

1. There is no standardization of NMEA color codes across
different manufacturers. Even Garmin uses different colors
on different units.

2. NMEA out on the Garmin 60C is BROWN, not white, according
to the 60C manual.

So GPS Brown to Navman Yellow. Best to follow the physical
root the ground connectors follow.


Perry posted 12-29-2005 08:00 PM ET (US)     Profile for Perry  Send Email to Perry     
Chuck, I meant to say that the Navman tech told me that the NMEA OUT is usually white.

I now have it wired like you said with the brown NMEA "OUT" from the GPS to the yellow NMEA "IN" to the Navman.

jimh posted 12-29-2005 09:45 PM ET (US)     Profile for jimh  Send Email to jimh     
You can get the NAVMAN 3100 manual on-line:

Page 17 shows the details of the NMEA wiring. You connect your GPS output to the NAVMAN input. The YELLOW wire on the pigtail from the Navman is the input signal; the black wire is the signal reference or common or battery negative. This is also confirmed on Page 19 in the table.

Page 17 also mentions the NMEA data required from the GPS: it wants a sentence with the data RMC. This is again repeated in the table on Page 19.

To connect your GPS to the NAVMAN:

--wire an NMEA-0183 output from the GPS to the yellow wire input. The NAVMAN has single-ended or unbalanced inputs. If the GPS has balanced or differential outputs (which will be labeled + and -), just connect the (+) wire to the NAVMAN's yellow input. Connect the common/ground/battery negative of both the GPS and the NAVMAN to the battery negative bus. If the GPS has differential outputs, do not connect the (-) lead of the differential output to ground. Follow these instructions no matter what someone else tells you! Never connect a differential output to ground!

--configure your GPS to transmit the NMEA sentence RMC on its output. Refer to the manual for your particular GPS. Generally you can select what data will be sent on a particular output. In my case my GPS has multiple outputs. I use one for the NAVMAN and a second one to transmit to my DSC radio.

--configure the NAVMAN to use the speed input from the GPS. This is explained in the manual on Page 13.

Perry posted 12-29-2005 10:53 PM ET (US)     Profile for Perry  Send Email to Perry     
Jim, as usual you provide excelent information.

I tested the Navman today and still have no communication between the GPS and the Navman. I will read through the info you posted after dinner. My manual is on my boat in the water.

I currently have the NMEA output from mt GPS (brown)connected to my yellow NMEA input oo the Navman. I also have the NMEA ground on the Navman joined with the common ground from the GPS connected to the battery negative.

I'm not sure if my GPS has differential outputs, I will have to research that tonite. I hope I can get them to work together.

Chuck Tribolet posted 12-30-2005 12:03 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Have you checked out that the GPS is set up to output NMEA?


Perry posted 12-30-2005 12:43 AM ET (US)     Profile for Perry  Send Email to Perry     
Yes Chuck I have and it is.

Upon furhter reading of both online manuals I have found out that my new Garmin 60c GPS supports NMEA 0183 version 3.01 and my new Navman 3100 fuel accepts NMEA 0183 version 2. I wonder if this is where the problem lies

Since they are both new and support NMEA 0183, I assumed they would be compatible. I will be very dissapointed if they are not because together, they were quite expensive.

I will try to contact Navman and Garmin tomorrow for help. Meanwhile, do you think this is the problem and if so am I screwed? Might one or the other devices be able to be reprogrammed to another version of NMEA 0183?

Perry posted 12-30-2005 01:06 AM ET (US)     Profile for Perry  Send Email to Perry     
Jim, Peter, and others, what brand of GPS are you using with your Navman 3100 fuel and do you know what version of NMEA 0183 the GPS supports?
Peter posted 12-30-2005 09:38 AM ET (US)     Profile for Peter  Send Email to Peter     
Perry -- I use a Garmin 182C as the speed input to my Navman 3100. I believe that my 182C uses NMEA 0183 version 3.

The Navman 3100 uses NMEA 0183's "RMC" (Recommended minimum specific GPS/Transit data) sentence to acquire speed information from the GPS. Almost any GPS made in the last 10 years, including the Garmin 182C and 60C, has this basic sentence in its "vocabulary". Thus, I doubt that the fact that the Navman and the Garmin use different versions of NMEA 0183 is the cause of any communication problems.

I would be looking at the interface setup of the Garmin to make sure its set to NMEA IN/NMEA OUT. Try the 4800 baud rate. Also, there are three Input options on the Navman (No/GPS/Sensor). Make sure that the Navman's Input is set to GPS.

Chuck Tribolet posted 12-30-2005 09:55 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Perry, your GPS does not have differential outputs -- I pulled
the manual down from Garmin's website. If it had differential
outputs, it would have NMEA OUT + and NMEA OUT - wires. It
just has "serial out", which means NMEA OUT, so it's single
ended (relative to ground), not differential.

What firmware level in the GPS? Latest is 4.00, from June.

And I agree with Peter, the NMEA level isn't the problem.
The only problems I've heard about with NMEA level have
been when the receiving unit (in the case the Navman) wanted
a higher level than the transmitter (GPS) was sending.

This gets curiouser and curiouser.

JMARTIN posted 12-30-2005 10:46 AM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
I have a Lowrance 335C DF. I am willing to bet that mine will work once I get the correct NMEA in wire connected. I know how to get to the communication menu on the Lowrance and how to set it. I think I can set a baud rate also.

Will I be able to test this thing inside a metal pole barn?
I doubt it, maybe the Navman screen for mpg will look differnt.

In case Navman is monitoring this thread,

(I am typing this in my most sarcastic "voice".)

So, your manuals for 2003 and 2004 are incorrect.

Who is putting these things together, the owner's wife?

Jeepers creepers guys, there is only 23 pages of instructions on mounting and installing a 3100. The only reason I bought this more expensive unit was for the GPS hookup. Is everybody else using the paddle wheel?


Peter posted 12-30-2005 11:23 AM ET (US)     Profile for Peter  Send Email to Peter     
You should be able to test the communication if you put the GPS into simulation mode and set the speed in the simulation. You should see that speed repeat on the Navman 3100 display.
Perry posted 12-30-2005 11:43 AM ET (US)     Profile for Perry  Send Email to Perry     
Peter, I have the GPS set to NMEA IN/NMEA OUT and 4800 baud rate. Also, I have the Navman's Input is set to GPS.

Chuck, so you tell me my GPS does not have differential outputs; does this mean I just connect the NMEA "OUT" wire from the GPS to the NMEA "IN" wire on the Navman or do I also join the ground wires together and connect them to a common ground from the battery?

Peter posted 12-30-2005 11:54 AM ET (US)     Profile for Peter  Send Email to Peter     
You should only have to connect the Garmin NMEA OUT to the Navman NMEA IN. You can join the ground wires of the two units and connect them to the battery ground but that shouldn't make any difference.
Perry posted 12-30-2005 08:34 PM ET (US)     Profile for Perry  Send Email to Perry     
Well, I spoke to a Garmin tech who told me to attach the NMEA "OUT" wire to the positive on a voltmeter and the ground wire to the black probe on the voltmeter to test if the GPS is sending info out. It had no jump in volts so I was told to send the GPS to Garmin for warranty repair so they can get it to output NMEA info to the Navman.

I then took my backup Garmin eTrex on the boat and jerry rigged it with wires to the Navman and voila, I had speed displayed on the Navman unit. I was relieved I was able to determine the problem was the GPS but dissapointed that I have to wait for it to be repaired.

Thanks all for your help and have a Happy New Year!


Chuck Tribolet posted 12-31-2005 01:26 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     

The ground wires have to be ultimately connected together back
at the battery, though, its best if the ground and NMEA wires
travel approximately the same path to reduce noise on the
NMEA connection.


jimh posted 01-01-2006 03:50 PM ET (US)     Profile for jimh  Send Email to jimh     
[Moved to this area.]
JMARTIN posted 01-01-2006 10:23 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
I am happy to report that my Navman and GPS are now talking. Yellow to yellow was the ticket and the simulation mode on the GPS to test. Thanks John
prm1177 posted 01-02-2006 01:13 PM ET (US)     Profile for prm1177  Send Email to prm1177     
Any use the Navman 3100 in a dual engine, single tank setup? I'm curious how easy it is to monitor the fuel flow from the single instrument.
Peter posted 01-07-2006 08:15 AM ET (US)     Profile for Peter  Send Email to Peter     
PRM1177 - Yes. My 27 has three tanks - one belly (170 gallons), two saddles (70 gallons each). Both motors can draw from any of the tanks at anytime depending on how I have the switches set up. About half of the operating time I have both motors drawing from the saddle tanks and the other half both motors drawing from the belly tank.

All of this has no bearing on how the Navman 3100 operates because each motor has its own fuel flow sender between the fuel filter and the motor monitoring fuel flowing to it. The fuel flow senders are connected together via a Navman supplied T-connector and the T-connector plugs into the sender input wire to the Navman 3100.

When the Navman 3100 is setup to monitor twin outboards, you can simultaneously see the fuel flow rate for each engine if you wish. It will also compute MPG based on the combined fuel flow rate of both engines. I typically leave the display set to read out MPG and speed. I probably look at the 3100's display more than any other instrument on the dash and adjust speed to achieve optimal MPG and comfort. It works quite well and I'm quite pleased with it. It helped me figure out which propellers were best for my 27.

Capt Bill posted 01-12-2006 01:52 PM ET (US)     Profile for Capt Bill  Send Email to Capt Bill     
Hello from San Diego, I am new to this forum, 1st timer submitting as well. Anyway, I 've been looking at fuel flow meters for quite a while - the navman 3100 in particular. I am admittedly a info junky. The more info I can from technology the better. So, the idea is to install the nav 3100 on my sea pro 190cc with 1999 125HP Merc 2 stroke from what I've read from you guys it should work pretty well. I do have one question - minor really - it is, does the main hour data accumulate over time or does it reset each trip?


Perry posted 01-12-2006 02:35 PM ET (US)     Profile for Perry  Send Email to Perry     
It has both trip hours and total hours in memory.
sid123456 posted 08-16-2006 07:50 PM ET (US)     Profile for sid123456  Send Email to sid123456     
Message boards are so great!!!!!! I, too, had a misprinted manual and spent a lot of time messing with the units. I called Navman and they didn't hint at a possible misprint. They kept referring to a yellow wire. As I was on my lunchbreak at work, I couldn't see how I'd had it wired, but I knew there was a yellow and a white wire. After reading this forum, I saw that I was wired into the output instead of the input (as my misprinted manual stated). Thanks so much for the posted info!


jimh posted 08-17-2006 09:17 AM ET (US)     Profile for jimh  Send Email to jimh     
Glad you found the information you needed. This article is now the NUMBER ONE search result on GOOGLE.COM for the terms "Navman 3100 wiring".
jimh posted 09-17-2006 08:53 AM ET (US)     Profile for jimh  Send Email to jimh     
[Fixed bad link to PDF file for NAVMAN 3100 Fuel Instrument in English.]
jimh posted 11-19-2006 09:19 AM ET (US)     Profile for jimh  Send Email to jimh     
Follow up on NAVMAN 3100 after two seasons:

I am still very happy with the NAVMAN 3100 FUEL instrument. This season I found a new use for it: a engine diagnostic tool.

In the middle of the boating season my engine began to have an intermittent problem. For about a month while I was tracking down the source of the problem and making repairs, the NAVMAN 3100 became a diagnostic tool. The actual problem was loss of ignition on one cylinder of my V6 outboard. As I discovered, a big V6 outboard can still run rather well on only five cylinders. An operator might not be aware that there was a significant problem because the motor still had sufficient power to operate the boat in a normal fashion. The best indicator that this problem was occurring was the NAVMAN 3100 FUEL instrument's reading of instantaneous fuel economy. When the engine was running on all six cylinders the fuel economy was at its normal reading, but as soon as the ignition problem occurred, there would be an immediate increase in fuel consumption. The NAVMAN 3100 FUEL instrument gave clear indication of when the engine was running properly and when it was not. Without it, it was often hard to tell with certainty if the engine was running on all cylinders. The boat speed and acceleration were almost the same, and, if the problem did not come and go as the boat ran at a steady speed, it was often hard to determine if the problem was present or not.

jimh posted 09-15-2007 11:13 AM ET (US)     Profile for jimh  Send Email to jimh     
I have now had my NAVMAN 3100 FUEL instrument in use for almost three seasons. I have found it to be a very valuable instrument. When I initially bought it I was thinking of it only as a source of real-time data about my engine's fuel consumption, however I have found that the NAVMAN is a wonderful record keeping tool. It accumulates the totals for the following parameters:


By logging this data you can compute the following averages:

--Miles per gallon
--Miles per hour
--Gallons per hour

Without the NAVMAN as my recording secretary I would never have collected this information. As a result I can now track several interesting trends with my boat and motor. Here is a summary:

Seasonal Data 2005
Gallons used = 508.7 gallons
Total log = 941.3 miles
Total hours = 67.3 hours

Average fuel economy = 1.85 MPG
Average speed = 14.0 MPH
Average fuel flow = 7.55 GPH

Seasonal Data 2006
Gallons used = 521.3 gallons
Total log = 908.7 miles
Total hours = 60.5 hours

Average fue economy = 1.74 MPG
Average speed = 15.0 MPH
Average fuel flow = 8.61 GPH

Seasonal Data 2005 and 2006
Gallons used = 1030.0 gallons
Total log = 1850 miles
Total hours = 127.8 hours

Average fuel economy = 1.80 MPG
Average speed = 14.5 MPH
Average fuel flow = 8.06 GPH

I will soon have the final figures from the 2007 season to add to these. Again, without the NAVMAN 3100 FUEL instrument I would have never collected this information.

jimh posted 02-07-2008 10:48 PM ET (US)     Profile for jimh  Send Email to jimh     
Here is the final data from the 2007 Boat Season as recorded by my NAVMAN 3100 FUEL INSTRUMENT:

Seasonal Data 2007
Gallons used = 359 gallons
Total log = 609.9 miles
Total hours = 60.9 hours

Average fue economy = 1.70 MPG
Average speed = 10.0 MPH
Average fuel flow = 5.9 GPH

Seasonal Data 2005 thru 2007
Gallons used = 1389 gallons
Total log = 2459.9 miles
Total hours = 188.7 hours

Average fuel economy = 1.77 MPG
Average speed = 13.0 MPH
Average fuel flow = 7.36 GPH

It appears that since NAVMAN has been sold to NAVICO, the NAVMAN brand has been melded into the NORTHSTAR line. However, it appears that the 3100 FUEL INSTRUMENT has been dropped from the catalogue. One reason for this may be due to a conflict with another fuel flow measuring and computing device, the LOWRANCE LMF 400. As it happens, the parent company, NAVICO, also owns LOWRANCE. Since LOWRANCE has their own fuel computer instrument, the 3100 may have been the odd man out in this corporate game of musical chairs.

GreatBayNH posted 02-08-2008 08:20 AM ET (US)     Profile for GreatBayNH  Send Email to GreatBayNH     
In the 2007 Defender Marine Buyers Guide it shows the old NAVMAN 3100 rebranded as the NORTHSTAR FUEL 310. Internet searched on the NORTHSTAR F310 will bring up some places that still have it, but you're right, it seems to have dropped from Northstar's line of product moving forward.
GreatBayNH posted 02-08-2008 09:21 AM ET (US)     Profile for GreatBayNH  Send Email to GreatBayNH     
The pricing on the LOWRANCE LMF 400 and LOWRANCE LMF 200 seems very reasonable. The LOWRANCE LMF 200 is more in line with all I need on my Montauk 170 but for only ~50 USD more you can get all the bells and whistles of the LOWRANCE LMF 400. The only reason I hesitate to go with the LOWRANCE LMF 400 is much of the functionality relies on sensor inputs that I do not currently have on my boat. I'd need to ugrade on my dated Garmin 162 to enjoy much of what the LOWRANCE LMF 400 has to offer, no?
Peter posted 02-08-2008 06:06 PM ET (US)     Profile for Peter  Send Email to Peter     
Aha. That explains why the 3100 has vanished from the face of the Earth. Too bad. Seems to me that to get an MPG readout from an LMF 400 display that you need to spend about $400 for the display, fuel probe and GPS receiver component (unless you already have a NMEA 2000 GPS receiver). A single engine NAVMAN 3100 could be had for about $250 to 275.
kamie posted 02-08-2008 06:50 PM ET (US)     Profile for kamie  Send Email to kamie     
that is exactly why when my Navman 3100 went on the fritz, I opted to purchase another one for $125 from Northstar. They will attempt to repair your 3100 and if they have the parts, not an issue but with mine the LCD had gone bad. I could have added fuel management to my NMEA-2000 but here is what I would need to add:
PN 763594 - SIM Module $254.44
PN 763672 - Fuel Kit $ 92.29

That along with either a new GPS or a transducer or GPS antenna and connectors.

jimh posted 02-18-2008 01:46 PM ET (US)     Profile for jimh  Send Email to jimh     
I had the chance to talk in person to Northstar at a recent boat show, and I asked them about the disappearance of the 3100 FUEL INSTRUMENT from the catalogue. The explanation given was there were problems with the LCD display from their supplier. They had to stop production due to lack of a suitable LCD display. The impression I got was they might restore this product to production if they work out the problems with supply of the LCD.

I told them I was very pleased with my 3100 FUEL INSTRUMENT and that it was my favorite electronic device on my boat, and I encouraged them to bring the 3100 FUEL back into production.

jmorgan40 posted 02-18-2008 02:45 PM ET (US)     Profile for jmorgan40  Send Email to jmorgan40     
Thanks for the update. That would explain why I was having trouble finding one online this weekend. I am still procrastinating on the fuek flow instrument and decided to go out and look at the 3100 one more time. I was not finding it available anywhere which made me wonder. I do not want the smaller one since I want to utilize the opening from the old speedometer that no longer works. Plus who needs it with the lowrance GPS unit.

Since I have the Lowrance 28HD i should just go with the Lowrance fuel flow guage and sender (LMF-400) The guage and sending unit is about $150. What do you think? I know you are happy with the Navman but I have not heard anything negative about the Lowrance unit either.

jimh posted 02-18-2008 07:55 PM ET (US)     Profile for jimh  Send Email to jimh     
Joe--At the time I purchased my 3100, the Lowrance device was not yet on the market. If I were in your situation and already had a Lowrance GPS with a NMEA-2000 network port, I would not hesitate to get the LMF-400 or LMF-200 gauge.
jmorgan40 posted 02-19-2008 05:31 AM ET (US)     Profile for jmorgan40  Send Email to jmorgan40     
Thanks Jim. I have not heard anything bad about the Lowrance unit so I think that will be the way I will go.
How about your fuel level. Does your revenge use the clear window in the floor or do you have an electric sending unit on yours to your Navman? Or do you just set the Navman when you fill up? guess it is not critical since I am more concerned with knowing my peak performance and fuel useage.
Thanks Again
Perry posted 02-21-2008 02:38 AM ET (US)     Profile for Perry  Send Email to Perry     
Jim, thanks for the update on the Navman 3100 fuel. I had to send mine in because of a problem with the LCD. They sent my old unit back without repairing it and said they would send me a new Northstar 310. That was 8 weeks ago. They said they have 6 units on their way from the manufacturer in New Zealand and I should get a new updated Northstar 310 soon. I hope it has an improved LCD.

The good news is that my old unit is on my boat and is working again. Some segments of the LCD flicker but I am still able to monitor my fuel flow and speed with it. I agree that it is a very usefull electronic device and I hope they decide to produce it again.

Perry posted 03-20-2008 12:47 AM ET (US)     Profile for Perry  Send Email to Perry     
Well, my new unit arrived today via FedEx 2nd day air at no cost. I thought it would be a new Northstar 310 fuel but, it is a new Navman fuel 3100s note the "s" after the 3100. It appears this unit has the new and improved display. It was made in New Zealand by Navman. I guess Navman is alive and well overseas including Europe and New Zealand. The unit has a slightly different look to it with a different Navman logo.

Since Northsar (NAVACO) purchased Navman here in the U.S. I wonder if they will market the 3100s and stick the Northstar name on it? I hope so, because I really think this is a cool device.

Here is a pic:

SJHOPTON posted 04-25-2008 06:13 PM ET (US)     Profile for SJHOPTON  Send Email to SJHOPTON     
I have a 3100 Fuel Navman, 2 years old. After powering off for 5 days or more, the memory is lost, it has to be re-programmed, ie: GPS input, Fuel size, Units, etc. Anyone come across this problem? Is there an internal battery that can be changed?
Perry posted 04-25-2008 10:41 PM ET (US)     Profile for Perry  Send Email to Perry     
There must be an internal battery to save data. Try call Navico (who bought Navman) technical support and ask a technican. The toll free number is 800-628-4487.
jimh posted 04-26-2008 12:16 AM ET (US)     Profile for jimh  Send Email to jimh     
By the way, I noticed that another NAVICO brand, SIMRAD, has some new devices which use a display that looks like it would be suitable for a 3100 FUEL instrument as well. I have to wonder if they're going to re-introduce the 3100 FUEL with this new display. See IS20-Instruments/IS20-Combi/

SJHOPTON posted 04-29-2008 02:47 PM ET (US)     Profile for SJHOPTON  Send Email to SJHOPTON     
Thanks for the number Perry, Navman said it is either a memory loss, (hardware), or software. Told me to try a system re-boot, by holding in the 2 center buttons when it gets powered up, I will have to recalibrate after, if that does not work then it is a memory failure, has to go to the shop for a new memory stick.
Perry posted 04-30-2008 01:59 AM ET (US)     Profile for Perry  Send Email to Perry     
You're welcome. I hope you get it to function correctly.
sid123456 posted 07-19-2008 08:47 PM ET (US)     Profile for sid123456  Send Email to sid123456     
I am trying to calibrate [a new NAVMAN 3100 FUEL installation] but I'm having problems. When I run six gallons from a pony tank my flow says around 7-GPH. When I switch back to the tank. The flow is 60-70 GPH and idle is 0. Anyone seen this? I'll call NAVMAN on Monday.
jimh posted 07-20-2008 09:46 AM ET (US)     Profile for jimh  Send Email to jimh     
I don't quite understand your narrative. Are you describing a situation where the calibration of the NAVMAN 3100 FUEL instrument appears to be affected by the nature of the fuel tank that is being used?
sid123456 posted 07-20-2008 10:52 AM ET (US)     Profile for sid123456  Send Email to sid123456     
I'm not sure what is affecting it. For calibration I used a small 6-gallon tank with the same size 3/8-inch hose. When calibrating, at wide-open-throttle (WOT) the flow is around 7-GPH. When I connect back to the master fuel tank, at WOT the flow is around 70-GPH. The strange thing is my old transducer was calibrated this way and it worked fine. Now with this new transducer I have tried to calibrate twice with the above result.
jimh posted 07-20-2008 11:31 AM ET (US)     Profile for jimh  Send Email to jimh     
Thank you for the further explanation.

Is it possible to change tanks with a fuel flow valve? If so, you ought to run on the main tank, and then switch to the 6-gallon while running. If the tank is truly the cause of the ten-fold change in the 3100 FUEL instrument's reading, it should show up immediately as you change tanks.

The only mechanism I can imagine by which the tank could affect the fuel flow transducer reading is through a change in fuel hose vacuum pressure. It may be that the fuel system suction is significantly different between the two tanks, and that this difference in vacuum pressure affects the transducer.

Please let us know what the technical support specialists at NAVMAN have to say about this.

tmann45 posted 07-22-2008 07:03 AM ET (US)     Profile for tmann45  Send Email to tmann45     
Could it be an air leak in the tank connection causing the problem? I don't know the type of transducer the NAVMAN uses, but the FloScan uses a spinning wheel and air in the line will upset the calibration.
jimh posted 07-22-2008 09:10 AM ET (US)     Profile for jimh  Send Email to jimh     
What is the effect of air in the fuel hose? Does it tend to make the fuel flow transducer wheel spin faster? Or slower?
Plotman posted 07-22-2008 09:16 PM ET (US)     Profile for Plotman  Send Email to Plotman     
What about sensor orientation?

The navman sensors need to be mounted so that the fuel hose is vertical, flowing from bottom to top. When you switched tanks, did you change this orientation?

tmann45 posted 07-23-2008 07:16 AM ET (US)     Profile for tmann45  Send Email to tmann45     
I think air in the line would tend to make the wheel spin faster.
sid123456 posted 08-06-2008 10:48 AM ET (US)     Profile for sid123456  Send Email to sid123456     
Tech support had no ideas. He said try a master reset. That made no difference.

When trying to calibrate the orientation of the transducer is the same.

sid123456 posted 09-12-2008 07:58 PM ET (US)     Profile for sid123456  Send Email to sid123456     
Navman sent me a new transducer. It's working fine now. I'll bet they're made in China. Faria has a new unit out and the transducer looks the same.
jimh posted 09-12-2008 08:04 PM ET (US)     Profile for jimh  Send Email to jimh     
Everything is made in China--except Boston Whaler boats, E-TEC motors, and Verado motors.
Peter posted 09-14-2008 05:39 PM ET (US)     Profile for Peter  Send Email to Peter     
After 4 1/2 years with the Navman F3100 on my 27 Whaler WD and no problems, I am now among those with a problematic flickering segments in the LCD display. The local boatshow is coming up and I will see if there is a Navico representative to speak with about this problem. I suspect given its age that I won't find much relief and if that is the case, then I will upgrade the major electronics for the boat next spring to a Garmin multi-function display (something like the 4210) which will display the same data that the F3100 does.

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