02 F225 Yamaha Round Fuel Mgmt Gauge - Trip Fuel Memory Resets when key turned off

[RangerBay]

I've been searching and going through schematics, and I can't find any really good info on these Fuel Management gauges aside from a basic wiring schematic and operating instructions. They are the round ones on non-networked engines for my '02 F225s

The wiring diagram I have shows a red wire with constant 12V, and I am getting 12V constant
The wiring diagram I have shows a yellow wire with 12V Key-On, which I am getting also.
The blue wire is the light circuit, which is energized with key-on (not on a switch).
I'm not sure what the other wires are for. Any ideas?

I have the wires connected as shown in the schematic.

However, every time I turn the key off, I lose the fuel used data, and it resets to zero. I maintain my miles traveled on my speedo gauge, but lose my total gallons used.
I'm just trying to get the 'memory' to work. Inevitably, when I get back to the ramp, and trailer, I kill the engines without looking at distance and fuel burn...so I cant calculate my fuel data. I can get distance out of my MFD, but because my engines arent NMEA, I cant track fuel without the yamaha fuel management gauge.

any input is appreciated

[boscoe99]

Have you verified that the red wire remains powered when the key is off and the battery switch is turned off?

If the red wire remains powered but the gauge loses its memory when the key is in the off position then I would suspect that the gauge has failed. Time for a new one.

[RangerBay]

Have you verified that the red wire remains powered when the key is off and the battery switch is turned off?

If the red wire remains powered but the gauge loses its memory when the key is in the off position then I would suspect that the gauge has failed. Time for a new one.

Yessir, it remains powered with the key off.
It does lose power when I turn off the battery switch, but that's expected. I don't turn off the battery switches until I get it home and charge it.

I was just wondering if there was another wire that had something to do with memory...although I figured it was all internal to the gauge.

I'll see if I can find a gauge. I wonder if I'd be better off just installing something that can read my fuel flow and display it on my EVO2 MFDs over NMEA 2k. I'll be repowering eventually, so hate to invest too much into the rigging on these older (but low hour and reliable) yamahas.

Thanks for your input!

[fairdeal]

wonder if I'd be better off just installing something that can read my fuel flow and display it on my EVO2 MFDs over NMEA 2k.

Navico makes a N2K fuel flow sensor - but you would need 2 of course.

https://www.hodgesmarine.com/Lowranc...-11517-001.htm

And then, AFAIK,
you also need an additional "module" for the MFD to "remember" how much fuel has been used

https://www.hodgesmarine.com/Navico-...-11522-001.htm

Cheaper to buy a brand new 6Y5 gauge:

https://www.boats.net/product/yamaha/6Y5-8350F-01-00

[boscoe99]

Don't know if this helps or not. I would take the "activated at the same time" comment with a grain of salt.

I might want to probe the red wire at the point where it enters the gauge itself to make sure that it is getting battery power. Your connector could be faulty. Not uncommon.

[RangerBay]

Don't know if this helps or not. I would take the "activated at the same time" comment with a grain of salt.

I might want to probe the red wire at the point where it enters the gauge itself to make sure that it is getting battery power. Your connector could be faulty. Not uncommon.

Thanks for the info. I'll check that red wire in a bit. It definitely has power where the bullet connectors are all joined. The gauge has a rubber plug on it where the wires enter. I'm tempted to try to pull it off and see if the circuit is visible and accessible for probing. I gently tugged on it the other day but didn't want to pull a wire out.

Any idea what the green wire and the green/white wire are sending/receiving from the tachs?

[RangerBay]

Navico makes a N2K fuel flow sensor - but you would need 2 of course.

https://www.hodgesmarine.com/Lowranc...-11517-001.htm

And then, AFAIK,
you also need an additional "module" for the MFD to "remember" how much fuel has been used

https://www.hodgesmarine.com/Navico-...-11522-001.htm

Cheaper to buy a brand new 6Y5 gauge:

https://www.boats.net/product/yamaha/6Y5-8350F-01-00

That Navico was my next step. I wasn't sure if the EVO2 was able to process the date without the additional module. I'll have to look into that more.

I may just get a used gauge.

[fairdeal]

Any idea what the green wire and the green/white wire are sending/receiving from the tachs?

rpms, of course - for the Sync function

[RangerBay]

rpms, of course - for the Sync function

duh...forgot about the sync.

[boscoe99]

There is a fellow that refurbishes Yamaha gauges. Mostly new lens' and polarizing filters I believe. You might want to contact him and see if he has any knowledge of the internal workings of the instrument. For all I know there could be a "mystery" fuse inside.
http://gaugesaver.com

[RangerBay]

There is a fellow that refurbishes Yamaha gauges. Mostly new lens' and polarizing filters I believe. You might want to contact him and see if he has any knowledge of the internal workings of the instrument. For all I know there could be a "mystery" fuse inside.
http://gaugesaver.com

I actually used him to refurb these gauges. I asked him around the same time I posted here. He just sent me an email back offering to ship me a gauge he has in stock, and if it works, he'll take my gauge in return at no charge (for parts, basically). Seems like a good deal.

[RangerBay]

FYI, sent to the guy at gaugesaver to swap my gauge and see if that was the problem.
Well, it worked. Apparently the 'memory' function on my gauge was no good. The new (used) gauge worked just fine.

[fairdeal]

Its nice to hear 'the rest of the story' - and glad that it turned out well.
I'm impressed with that 'gaugesaver' guy -
seems he does good work - and he is addressing something that was an unmet need.

[FabricGATOR]

FYI, sent to the guy at gaugesaver to swap my gauge and see if that was the problem.
Well, it worked. Apparently the 'memory' function on my gauge was no good. The new (used) gauge worked just fine.

Good on ya RangerBay !
Thanks for returning and giving us an update.
Perhaps now, the next time this comes up, that one of us may remember your report and cure.
FWIW, I have my batteries completely isolated and I know that they have been fully off and removed this week for several days. Yesterday, my fuel memory was still the same consumed gallons as I remember.
Possibly, they have a coin battery inside and your reached its useful limit.
Anyhow, thank you for the finale'...
Cheers!