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Author Topic:   NAVMAN F2100 Accuracy
FISHNFF posted 07-11-2010 02:33 PM ET (US)   Profile for FISHNFF   Send Email to FISHNFF  
I just mounted a NAVMAN F2100 [fuel flow instrument] with a FS45 transducer on my 1988 Boston Whaler OUTRAGE boat with Yamaha F115. I mounted it following the manufacturer's directions, but I get very inaccurate readings. At maximum throttle it will read around 38-GPH! At idle it reads 2-GPH. In big red letters, it says, "Installation of NAVMAN not for engines with a fuel return line." Is this my problem?

A buddy with an 1987 Outrage 18 and a Suzuki DF140 has the same NAVMAN with no problems.--FISHNFF

acseatsri posted 07-11-2010 03:41 PM ET (US)     Profile for acseatsri  Send Email to acseatsri     
It sounds like you're set for liters per hour. Mine is nearly spot on all the time, within a gallon per 100 gallons burned.
jimh posted 07-11-2010 07:40 PM ET (US)     Profile for jimh  Send Email to jimh     
Even with the out-of-the-box default calibration, the fuel flow measurement of a NAVMAN F2100 fuel instrument should be accurate to within ten percent. I have been using a NAVMAN fuel flow instrument for several years. Currently I have it calibration against another device which I believe is very accurate. Once calibrated the two devices show fuel flow with very little variation within the specified range of the NAVMAN.

The specifications for the NAVMAN limit the lower volume of fuel that can be accurately measured, and as a result if your engine idle speed fuel flow is very low, the NAVMAN will probably not give an accurate reading. Typically the NAVMAN must have a flow rate of about 0.5-GPH to begin to have accuracy. The accuracy will also tend to suffer at very high flow rates. As a result, it is my experience--this is based on using the device for five years--that the NAVMAN fuel flow reading will be lower than it really is at low volumes, about right at mid-ranges, and higher than it really is at high volumes.

When you install the NAVMAN you have the ability to alter the fuel flow calibration. Before you undertake any change, I suggest you collect some data about the current setting and arrive at an estimate of its accuracy. Then make a calibration change, collect some more data, and re-evaluate the accuracy. I followed this procedure, and after two adjustments to the calibration achieved rather good accuracy from the NAVMAN.

There is no way for me to know if your problem is related to having a return fuel line. I have no idea if your boat has one. Perhaps you could tell us.

jimh posted 07-11-2010 07:44 PM ET (US)     Profile for jimh  Send Email to jimh     
[This discussion of small boat electronic devices has been moved to SMALL BOAT ELETRICAL from another area.]
jimh posted 07-11-2010 08:11 PM ET (US)     Profile for jimh  Send Email to jimh     
NAVMAN as a maker of fuel flow instruments is defunct. After Brunswick bought them, they ended up with a bad case of corporate neglect, and were eventually sold off to NAVICO. NAVICO moved the NAVMAN line into their other brands, dropping the NAVMAN name. The current model of fuel flow instrument most similar to the old NAVMAN F2100 is the Northstar F210. The specifications for the Northstar F210 fuel instrument call for the range of flow accuracy to be

0.5 to 43 US gallons per hour


This confirms what I mentioned above about the flow rate error at low flow volume. A modern 115-HP engine can idle at less than 0.5-GPH flow rate. (My 225-HP engine idles at 0.2-GPH.) As a result, the F210 or F2100 may not show an accurate fuel flow reading until the flow rate rises above 0.5-GPH.

As for the notion you have set the units to the wrong setting, liters instead of gallons, we might see if that makes any sense. Your 115-HP engine should be consuming about 10-GPH or more at maximum throttle. 10-GPH is the same volume as 37.85-liters-per-hour. Maybe you should read the manual and check on how you have set the units.

FISHNFF posted 07-11-2010 10:19 PM ET (US)     Profile for FISHNFF  Send Email to FISHNFF     
Page 6 in the manual. "Instrument SetUp."

That was it.
Thanks all.


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