Fuel Gauges Not Working Properly--Manual Calculation Method?

GradyChris

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#1
Hi Everyone,
I don't believe that my fuel gauges are working properly on either the AUX or Main tanks on my new to me 98 272 Sailfish.
Twin OX66 225 Yamahas with all the original Yahama gauges.
I understand that this is a somewhat common problem and many folks don't solely rely on their fuel gauges even on brand new boats.
The miles per gallon gauge does seem to work or at least was reading in the general range of what I expected (0.8-1.2 mpg) in the few times I had the boat out last Fall after I bought it.

Would it be an okay/acceptable practice to just log my miles traveled (off the chartplotter or perhaps some other phone app) and assume a conservative 0.6/mpg or so fuel burn and every 100 miles or so fuel back up?

Figure just run off the main tank most of the time (150 gals) with occasional use of the aux just to keep the fuel fresh.

Other ideas/methods folks use?
 

DennisG01

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#2
What do you mean by "not working properly"? It's not uncommon for a gauge reading to be slightly inconsistent from F to E, but it should be relatively consistent from fill-up to fill-up.

You could certainly manually log your miles.
 

GradyChris

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#3
Fuel level not moving on either tank...aux shows too high, main shows too low
i.e. the levels barely ever change despite how many miles I've gone. I accidentally ran out of fuel once last yr and had to get towed in
 

glacierbaze

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#4
Install an in-line fuel transducer, which gives you read out on your GPS. Program the GPS to tell it your tank capacity, and it will give you gallons used, or gallons remaining, and accurate MPG. Re-set to full when you gas up.
Otherwise, besides keeping a manual trip log, doesn't your GPS and your Yamaha gauges have a trip log mode?
 
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GradyChris

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#5
Install an in-line fuel transducer, which gives you read out on your GPS. Program the GPS to tell it your tank capacity, and it will give you gallons used, or gallons remaining, and accurate MPG. Re-set to full when you gas up.
Otherwise, besides keeping a manual trip log, doesn't your GPS and your Yamaha gauges have a trip log mode?
Thanks---both the Yamaha gauges and my raymarine chartplotter and backup Garmin GPS can calculate miles along with so I'll do that there. I'll look into the fuel transducer for a possible upgrade for next season...that seems like a nice add.

Hopefully I can average closer to 1.2 vs the 0.8 I saw a lot of the few times I ran the boat last yr....bottom was extremely dirty and fouled with barnacles when I bought it though so fresh paint should help me out a bit too
 

DennisG01

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#6
OK, try this to diagnose...

-- At each fuel sender, disconnect the pink wire (this goes to the gauge) and touch it to the tank ground (the tank ground is there and properly connected, right?). With the key 'on', the gauge should read 'full' (note, it takes a few seconds for the gauge to respond).
-- With the pink wire simply removed, the gauge should read 'empty'.
-- The aux tank may use a different color, but it will still be attached to the sender.

If that checks out, then the wiring and gauge are good and the sender is the issue. Replace sender, go boating. If the gauge doesn't respond, then the issue is with the pink wire (you verified ground, right?) or the gauge.
 

grady23

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#7
replace your old senders with the ones from WEMA. great price and VERY GOOD units Be sure to specify SAE screws or both. DO NOT use and electric drill to do this job as the open fuel tank represents an explosion hazard. WEMA.COM. Be sure to clean all wiring contacts. The original senders are crap.
 

Magic

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#8
New question, similar problem. Gauge is flashing one bar, just need to confirm the wring/colors from the gauge end, but can't find any wiring schematics for the Chase 26 CC. Red & Black from the Sender, go to ??? from the Gauge side. Thanks.
 

Deep Blue

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#9
Install an in-line fuel transducer, which gives you read out on your GPS. Program the GPS to tell it your tank capacity, and it will give you gallons used, or gallons remaining, and accurate MPG. Re-set to full when you gas up.
Otherwise, besides keeping a manual trip log, doesn't your GPS and your Yamaha gauges have a trip log mode?
Glacierbaze,
do you have a manufacturer / model? My Sailfish is a 2003 so it was pre-NMEA but I have a modern Garmin chartplotter and could run the necessary wires.

Thanks.
 

Magic

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#10
1999 Twin 225's Yamaha's. Just looking to get the wiring straight first. Sender/Fuel Gauge worked fine when we put the boat away, but when we first powered up the gauge isn't working, just one flashing bar. I was concerned that my boat partner cross the wires when he tried cleaning up the wiring to debug the problem. Thanks.
 

SkunkBoat

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#11
The standard for fuel gauge wires is pink (pink & white for aux). If you have a red wire on the sender, someone replaced the wire.
I have seen pink discolor to orange-ish with age but never to red.
 

Magic

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#12
Thanks for your help. After spending several hours debugging the wiring from the sender to the gauge, we found that the main grounding wire was mistakenly put on the positive terminal by the yard when they commissioned the boat! Moved to the the negative post and the gas gauge worked!