Internal fuel tank gauge & panel gauge synchronization

Is there a way to get the panel fuel gauge to match what is really in the tank and what the internal tank gauge reads? My internal gauge in buried beyond the full mark (when full) and my panel gauge reads almost ¾ full.

Re: Internal fuel tank gauge & panel gauge synchronization

Its all about measring resistance.<br /><br />Try to use trimpot (adjutable ristance, cost about 1$ for 10K ohm).<br /><br />Hook it up to the white and black cable, see tune it so that the reading show exactly full, soo that last bar lights up.<br />- Meassure the resitance you got, take note of it (R full).<br /><br />Change the ristance so it just start to flash on the lowest bar (almost empty). <br />- Again take note of that resistance (R empty).<br /><br />If you want, adjust the pot so you get half full reading and take note of that (R half).<br /><br />Now check what ever resiatnce you get from your sender in different position, empty (r empty), full (r full) and half full (r half).<br /><br />Do they match? (Probaly note since you added this topic)<br /><br />Now you have to take your knowledge of resitance calculations (if you have any).<br /><br />If you put two resistors in series you just add their values togheter, this can help you with an offset problem by adding one static resitor (cost a penny).<br /><br />If you add two resitors in parallel you have to use more complicated formula:<br /> 1/R = 1/r1 + 1/r2<br />or expressed like this:<br /> R = 1 / (1/r1 + 1/r2)<br /><br />Where R is the result, r1 could be your fuel senders ristance, r2 could be a static resistor.<br /><br />Now you you just have combine these rules to find a combination that gives the result you want. (r full => R full, r empty => R empty).

Re: Internal fuel tank gauge & panel gauge synchronization

Wow, I need to be an engineer to fiqure this one out. I thought there would be a simple tweak adjustment built into the system. I have an analog gauge on the dash, not bars like you mention in the newer style Yamaha set up.

Re: Internal fuel tank gauge & panel gauge synchronization

I have a similar problem with a used boat 1997 Sea Pro 23.5 WA with 1997 Yamaha 200 SW II.<br /><br />When my digital Yamaha fuel gage reads one bar [empty] I can take only 45 gal in a 120 gal tank?<br /><br />I also have an analog gage on the dash not hooked up. I understand both gages can not work at the same time. <br /><br />Does the analog gage have the same resistance requirements as the Yamaha digital display?<br /><br />I have not checked the resistance of the sending unit. When it stops raining I will pull the sending unit and read the resistance...<br /><br />Thanks,<br /><br />ps I have never run out of gas ... yet.

Re: Internal fuel tank gauge & panel gauge synchronization

fishon71,<br /><br />If you have the analogue one its the same principle, but of course the full reading would be the same as your highest dial, and the empty would be your lowest. The analogue is more "presize" (the digital one has only like 8 steps/bars) <br /><br />I don't remeber which way it goes, if disconnected wires (infinit resistance) give you full tank, I belive that this was the case. And if you connect the white and black (zero resistans) you get empty tank.<br /><br />Then you "just" have to add some resistans to reach full tank on the dial when the tank is full.<br /><br />Maybe there is some adjustment that can be done on the fuel level sender itself.

Re: Internal fuel tank gauge & panel gauge synchronization

jasell, <br /><br />(fishon71, I jump in here in this thread since I have same problem as You, hope You do not mind)<br /><br />I have a Yamaha digtal speedometer (I have a Yamaha F115, 2003) that include a vertical 8 segments fuel meter.<br /><br />My tank is 80 liter/21 US gal.<br />When my fuel meter shows 4 segments (1/2) there is actually only 20 liter/5 gal in the tank.<br />A rather large missreading.<br /><br />My Yamaha dealer tried to correct this but did not manage (I do not know if they just said that or actually tried to solve this warranty case and did not manage to solve it).<br />So I probably have to fix this by myself.<br /><br />I find it somewhat strange the Yamaha digital guage do not have any easy way to control this. There is a selector switch at the back of the digital speedometer that should control readings but the Owners manual say nothing more how this switch should be set.<br /><br />Do You think I can correct my fuel sender reading by changing something in the digital guage or do I need to do the "resistance test" and calculation You described above so it can show actual volume in the tank?<br /><br />The boat is rather new, 2003, and had this fuel guage "defect" from day 1. I have talked to another person that has same boat and outboard as me and he has same problem with fuel meter.<br /><br />Thank's in advance!

Re: Internal fuel tank gauge & panel gauge synchronization

Not being an expert on the topic I tell you what I know and can guess (I have a degree in engineering).<br /><br />- I don't use the fuel meter my self, I have three seperate fueltanks that is easier to get to the gas station for my type of boating.<br /><br />- To your question, boths the tach and the speedo meter has switches. I only seen some old info about the function of the one at the Tach, it has to be set according to the size of the engine to get correct rpm reading, different engines give different number of pulses per revolution.<br /><br />- I have searched Yamaha for the function of the switch and posted the question on some forums like this, no one had a clue (no answers than let them be).<br /><br />- The fuel senders are typical a rod with a float running up and down. Depending on the postion of the float you get different resistans from the sender. So let's say that you got the "correct" sender for your instrument, the max and min resistance corresponds to what your instrumnet when you have it dismounted.<br />But when the sender is mounted in the tank you ge too low readings, it says to me that the mouting postion of the sender isn't optimal, it sits to high. You could adress this with just adding a resistor, but that might prevent you from having a Zero reading.<br /><br />If the shape of your tank was very odd (Wide in the top and narrow in the bottom) you could have correct reading on max and min but the half tank reading could be given even though the tank was nearly empty, if you understand what I mean.<br />This is very hard to correct, you need the variable ristance to match the geometry of your tank, some car manufactures do this either "electronic" in the cpu or with some special resistors.<br /><br />-I would guess that "playing" with the switches doesn't harm your instrument, so just take a note of the original postions for the switches. Then try different settings and move the fuel sender in different positions to see if the behavior is changeing. I would be intressted in your findings...<br /><br />Good luck

Re: Internal fuel tank gauge & panel gauge synchronization

Check page 2-14 (page 37) and 2-16 (page 39) in the owners manual for the 115-150 hp.<br /><br />Two of the switches are used for speed units and the other (two I guess) are for the fuel sender, apparantly Yamaha fuel sender doesn't work as other fuel senders.<br />It just says "consult your Yamaha dealer for correct setting"...

Re: Internal fuel tank gauge & panel gauge synchronization

I have found that many times the trick to making fuel guages more accurate is to run a seperate ground from the battery to both the guage and the fuel sending unit.

Re: Internal fuel tank gauge & panel gauge synchronization

Ray has good advice but from another engineer, just remember, you can play around with these things all you like but they are never precise and the reading you get will be affected by the physical attitude of your boat. Get to know the readings when stationary on the water and how much fuel you can add to completely fill. You will eventually know when you are running low. Fuel guages are always inaccurate, at best an indicator and not to be trusted..real bummers.