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Author Topic:   Navman 3100 calibration method

JMARTIN posted 03-23-2005 07:32 PM ET (US)
I can see some problems with the calibration method that Navman recomends for thier fuel flow meter, and they say you have to calibrate it, and more than once. They want me to put a known amount of fuel in a tank and run her out and then "correct" what the Navman said has gone out. They suggest at least 4 gallons. OK, I put 4 gallons in a portable tank, I guess I can use my kicker tank, hope there is no crud in it since I will suck right to the bottom with no filter. Navman also says, put the sending unit past the filter, the will not replace the sending unit if you suck up crud into it. I am going to have to get a new fitting to hook up to the tank or a new hose and fitting and then I can use my existing filter. So now I am out in the sound, running at cruising speed for about 1/2 an hour to use up the 4 gallons and it goes dry and the motor quits. I thought you were suppose to refrain from running a VRO out of fuel, but any how there I am dead in the water. Hope I don't get run over by a ferry, or a barge, or start to drift onto the rocks. Well I guess I have to reconnect the main fuel tank up and hope everything picks up and works OK. Hope I do not spill too much gas reconnecting the hose. I can't use the kicker because it's tank is out of fuel. Or I can buy another portable tank or something. Anybody done this? Is there not a better way?
Stupid question: Can you run a 200 looper OMC off a 6 gallon portable tank? For some reason I am worried about fuel starvation or venting problems doing so. John

Chuck Tribolet posted 03-23-2005 09:18 PM ET (US)
You shouldn't spill any gas with a QD fitting. And you should
have them on both tanks and both fuel lines, so in a pinch you can run the kicker off the main tank, or use the kicker tank
for a backup for the main engine.
I'd prop up the kicker tank so the pickup is in the lowest
corner. And put some fuel in first, run it dry, THEN make
the calibration run.
I've never heard "don't run a VRO out of fuel". I have heard
"don't run an injected motor out of fuel".
Venting won't be a problem. Fuel starvation shouldn't be
a problem as long as you have a reasonable diameter hose and
don't run wide open, just cruise. If it doesn't run right,
shut it down right away, and use the big tank till you figure
out what's what.

Chuck
where2 posted 03-23-2005 11:12 PM ET (US)
VRO says don't run it out of fuel because at the point you start running air through the VRO pump your mixture goes high toward the oil content.
The prudent way to calibrate the fuel flow gauge is using the built-in tank, presuming you intend to use this all the time anyway. The greater the amount of fuel consumed during your calibration proceedure, the lower your margin for error.
Say you have a 60 gallon built-in tank. Your fuel gauge reads 1/2 full. You fill up the tank to just where it starts to overflow out the vent (being environmentally friendly using one of those little spill catcher jugs on your vent line so you don't pollute the lake). Now, you go boating and use 30 gallons by the flow meter. You get back to the fuel station and add 28.4 gallons of fuel to put you back at the just overflowing stage. At that point, you're off by a 5.3% error. At that same error rate, on 4 gallons of fuel, you're looking at 0.22 gallons (28oz) of fuel. Without running the engine dry, finding and measuring that last 0.22 gallons of fuel and recalibrating the gauge is going to be more difficult than finding the measuring the 1.6 gallons had you run 30 gallons through the meter.
I know we'd all like the new gauge to be accurate to 1% on the day we install it, but without an additional calibrated fuel flow gauge to compare it to, you have to use the method Navman suggests and run some fuel through the gauge and replace it with a known quantity. The larger the quantity of fuel you use, the better your chances of getting the calibration closer to actual fuel used.
The other reason you don't want to run the tank completely dry is that Navman's flow transducer gets confused by bubbles in the fuel flow and fouls up the measurement to the gauge in the first place.
Yamaha's fuel management gauge uses a similar method to calibrate it, it's not an "uncommon" method.
If you could use a 6-gallon portable tank and run roughly 4 gallons out of it, then carry it back to the filling station and put exactly the same amount back into the tank as you burned, you could approximate your consumption without running the system dry. However, being off 0.22 gallons is 5.3% if you only burn 4 gallons. Getting the "exact" same amount of fuel back into the 6 gallon tank within one quart is going to be challenging.
JMARTIN posted 03-24-2005 04:57 PM ET (US)
Thanks for the replies. I have asked Navman the same question and we will see what they say. My kicker uses premix and the main does not so the hose switching is not a good option. I am paranoid about running out of fuel so I seldom let my fuel get to a 1/4 tank. Unless Navman has a better idea, I will start with a vent spitting full, run like normal, refill to a vent spitting full and repeat untill I think I am getting pretty good readings. The main reason I bought the flow meter was to try to optimize fuel economy with the secondary reason that the Revenge's fuel guage has given me all sorts of funny readings and I do not trust it. Hey Mike, what are you doing with your Navman and Revenge? John
Mike Brantley posted 03-24-2005 11:31 PM ET (US)
Sounds like we're going through the same thing. I had hooked up a six-gallon tank, but then I decided that was too much of a pain and just decided I would calibrate to the best of my ability using the built-in tank. At no point do I think I will be in the mood to run out of fuel. That would surely happen at the worst time. So I topped off the tank to the point of a small amount of vent spillage. According to the Navman 3100, I have burned about 15 gallons so far. Once I've used a little more, I will fill up again and see how much discrepency there is. I'll watch it closely a few times until, like you say, I feel good about the readings.
If I can't get it perfectly accurate, so be it. Like you, I like to keep plenty of fuel in the tank and don't run it too low.
Meanwhile, my gas tank has premix in it, and I have connected the OMC/BRP VRO system. (How's that for Alphabet Soup?) So I am burning a rich mix and getting plenty of smoke and fumes. The system seems to be drawing the proper amount of oil from the VRO tank, and I will be really sure of this after a few more gallons of fuel is consumed. Then the fuel tank will get straight gasoline.
You said Navman recommends putting the fuel flow sender after the filter, and that made be say "Uh, oh." Mine is before the filter, and I don't really feel like moving it now. I'll see what happens.
I like the Navman 3100 very much by the way, and I'm glad I went with it over the particular FloScan unit I had been considering.
Jerry Townsend posted 03-25-2005 01:42 AM ET (US)
Using the main tank works well - and realize that repeated "calibrations" refines and corrects the calibration so that after doing this a few (three or four) times, the calibration should be right on. ---- Jerry/Idaho
Backlash posted 03-25-2005 09:09 AM ET (US)
Mike,
The reason Navman (and I'm sure Floscan) recommends installing the fuel flow sensor after the fuel filter is to keep any crud out of the sensor. The sensor should also be mounted vertically with the intake up.
Steve
JMARTIN posted 03-25-2005 12:29 PM ET (US)
Navman said it will take 3 to 4 days to respond and I will post what they say. Now I am concerned about how to put my fuel flow sensor on. My filter is above and towards the stern of the starboard bilge access, where the internal tank fittings come out. It is mounted with these big old hurking bolt looking things that are pitted and rusted. I have sealed around the bolts and painted them because they looked so scary. I do not think that moving the filter is a good option. The problem is, that in order to install the sensor vertically, I have to have the fuel hose do two 90 degree bends in a tiny amount of space. I am worried about kinking the hose. Maybe I can get a right angle fitting for the filter outlet and have the inlet hose do a gradual 180 degree bend to the sensor and then a 90 back out. I am getting really close to the transom and I am worried about the sensor and the fittings being constantly wet from spray. John
JMARTIN posted 03-30-2005 02:44 PM ET (US)
Update: Navman responded to my calibration concerns. They basically said what we figured out, start with the main tank full, cruise as normal, refill the tank full, and adjust the Navman to how much fuel you put in, repeat. I also got the sensor installed as per instructions. What helped was I purchased new fuel hose and it is much easier to bend with out kinking than the old stuff that has been exposed to the elements for years. Now to figure out how to hook up the power and the GPS to the Navman. The instructions are a little vague and of course the instruction book for the GPS and the book for the Navman explain it differntly. John
PS Pet Peeve: I do not know why some manufactures do not send you everything that you need part wise for installation. Navman sends the hose clamps for the sensor, but not the (required) 1 amp in line fuse set up for the power. John

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Author	Topic: Navman 3100 calibration method
JMARTIN	posted 03-23-2005 07:32 PM ET (US) I can see some problems with the calibration method that Navman recomends for thier fuel flow meter, and they say you have to calibrate it, and more than once. They want me to put a known amount of fuel in a tank and run her out and then "correct" what the Navman said has gone out. They suggest at least 4 gallons. OK, I put 4 gallons in a portable tank, I guess I can use my kicker tank, hope there is no crud in it since I will suck right to the bottom with no filter. Navman also says, put the sending unit past the filter, the will not replace the sending unit if you suck up crud into it. I am going to have to get a new fitting to hook up to the tank or a new hose and fitting and then I can use my existing filter. So now I am out in the sound, running at cruising speed for about 1/2 an hour to use up the 4 gallons and it goes dry and the motor quits. I thought you were suppose to refrain from running a VRO out of fuel, but any how there I am dead in the water. Hope I don't get run over by a ferry, or a barge, or start to drift onto the rocks. Well I guess I have to reconnect the main fuel tank up and hope everything picks up and works OK. Hope I do not spill too much gas reconnecting the hose. I can't use the kicker because it's tank is out of fuel. Or I can buy another portable tank or something. Anybody done this? Is there not a better way? Stupid question: Can you run a 200 looper OMC off a 6 gallon portable tank? For some reason I am worried about fuel starvation or venting problems doing so. John
Chuck Tribolet	posted 03-23-2005 09:18 PM ET (US) You shouldn't spill any gas with a QD fitting. And you should have them on both tanks and both fuel lines, so in a pinch you can run the kicker off the main tank, or use the kicker tank for a backup for the main engine. I'd prop up the kicker tank so the pickup is in the lowest corner. And put some fuel in first, run it dry, THEN make the calibration run. I've never heard "don't run a VRO out of fuel". I have heard "don't run an injected motor out of fuel". Venting won't be a problem. Fuel starvation shouldn't be a problem as long as you have a reasonable diameter hose and don't run wide open, just cruise. If it doesn't run right, shut it down right away, and use the big tank till you figure out what's what. Chuck
where2	posted 03-23-2005 11:12 PM ET (US) VRO says don't run it out of fuel because at the point you start running air through the VRO pump your mixture goes high toward the oil content. The prudent way to calibrate the fuel flow gauge is using the built-in tank, presuming you intend to use this all the time anyway. The greater the amount of fuel consumed during your calibration proceedure, the lower your margin for error. Say you have a 60 gallon built-in tank. Your fuel gauge reads 1/2 full. You fill up the tank to just where it starts to overflow out the vent (being environmentally friendly using one of those little spill catcher jugs on your vent line so you don't pollute the lake). Now, you go boating and use 30 gallons by the flow meter. You get back to the fuel station and add 28.4 gallons of fuel to put you back at the just overflowing stage. At that point, you're off by a 5.3% error. At that same error rate, on 4 gallons of fuel, you're looking at 0.22 gallons (28oz) of fuel. Without running the engine dry, finding and measuring that last 0.22 gallons of fuel and recalibrating the gauge is going to be more difficult than finding the measuring the 1.6 gallons had you run 30 gallons through the meter. I know we'd all like the new gauge to be accurate to 1% on the day we install it, but without an additional calibrated fuel flow gauge to compare it to, you have to use the method Navman suggests and run some fuel through the gauge and replace it with a known quantity. The larger the quantity of fuel you use, the better your chances of getting the calibration closer to actual fuel used. The other reason you don't want to run the tank completely dry is that Navman's flow transducer gets confused by bubbles in the fuel flow and fouls up the measurement to the gauge in the first place. Yamaha's fuel management gauge uses a similar method to calibrate it, it's not an "uncommon" method. If you could use a 6-gallon portable tank and run roughly 4 gallons out of it, then carry it back to the filling station and put exactly the same amount back into the tank as you burned, you could approximate your consumption without running the system dry. However, being off 0.22 gallons is 5.3% if you only burn 4 gallons. Getting the "exact" same amount of fuel back into the 6 gallon tank within one quart is going to be challenging.
JMARTIN	posted 03-24-2005 04:57 PM ET (US) Thanks for the replies. I have asked Navman the same question and we will see what they say. My kicker uses premix and the main does not so the hose switching is not a good option. I am paranoid about running out of fuel so I seldom let my fuel get to a 1/4 tank. Unless Navman has a better idea, I will start with a vent spitting full, run like normal, refill to a vent spitting full and repeat untill I think I am getting pretty good readings. The main reason I bought the flow meter was to try to optimize fuel economy with the secondary reason that the Revenge's fuel guage has given me all sorts of funny readings and I do not trust it. Hey Mike, what are you doing with your Navman and Revenge? John
Mike Brantley	posted 03-24-2005 11:31 PM ET (US) Sounds like we're going through the same thing. I had hooked up a six-gallon tank, but then I decided that was too much of a pain and just decided I would calibrate to the best of my ability using the built-in tank. At no point do I think I will be in the mood to run out of fuel. That would surely happen at the worst time. So I topped off the tank to the point of a small amount of vent spillage. According to the Navman 3100, I have burned about 15 gallons so far. Once I've used a little more, I will fill up again and see how much discrepency there is. I'll watch it closely a few times until, like you say, I feel good about the readings. If I can't get it perfectly accurate, so be it. Like you, I like to keep plenty of fuel in the tank and don't run it too low. Meanwhile, my gas tank has premix in it, and I have connected the OMC/BRP VRO system. (How's that for Alphabet Soup?) So I am burning a rich mix and getting plenty of smoke and fumes. The system seems to be drawing the proper amount of oil from the VRO tank, and I will be really sure of this after a few more gallons of fuel is consumed. Then the fuel tank will get straight gasoline. You said Navman recommends putting the fuel flow sender after the filter, and that made be say "Uh, oh." Mine is before the filter, and I don't really feel like moving it now. I'll see what happens. I like the Navman 3100 very much by the way, and I'm glad I went with it over the particular FloScan unit I had been considering.
Jerry Townsend	posted 03-25-2005 01:42 AM ET (US) Using the main tank works well - and realize that repeated "calibrations" refines and corrects the calibration so that after doing this a few (three or four) times, the calibration should be right on. ---- Jerry/Idaho
Backlash	posted 03-25-2005 09:09 AM ET (US) Mike, The reason Navman (and I'm sure Floscan) recommends installing the fuel flow sensor after the fuel filter is to keep any crud out of the sensor. The sensor should also be mounted vertically with the intake up. Steve
JMARTIN	posted 03-25-2005 12:29 PM ET (US) Navman said it will take 3 to 4 days to respond and I will post what they say. Now I am concerned about how to put my fuel flow sensor on. My filter is above and towards the stern of the starboard bilge access, where the internal tank fittings come out. It is mounted with these big old hurking bolt looking things that are pitted and rusted. I have sealed around the bolts and painted them because they looked so scary. I do not think that moving the filter is a good option. The problem is, that in order to install the sensor vertically, I have to have the fuel hose do two 90 degree bends in a tiny amount of space. I am worried about kinking the hose. Maybe I can get a right angle fitting for the filter outlet and have the inlet hose do a gradual 180 degree bend to the sensor and then a 90 back out. I am getting really close to the transom and I am worried about the sensor and the fittings being constantly wet from spray. John
JMARTIN	posted 03-30-2005 02:44 PM ET (US) Update: Navman responded to my calibration concerns. They basically said what we figured out, start with the main tank full, cruise as normal, refill the tank full, and adjust the Navman to how much fuel you put in, repeat. I also got the sensor installed as per instructions. What helped was I purchased new fuel hose and it is much easier to bend with out kinking than the old stuff that has been exposed to the elements for years. Now to figure out how to hook up the power and the GPS to the Navman. The instructions are a little vague and of course the instruction book for the GPS and the book for the Navman explain it differntly. John PS Pet Peeve: I do not know why some manufactures do not send you everything that you need part wise for installation. Navman sends the hose clamps for the sensor, but not the (required) 1 amp in line fuse set up for the power. John