Yamaha Fuel Gauge issue

SeaVee

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#1
All,

I have a 2001 265 Express with 2x200 HPDI’s (‘01’s). Boat has a 130 gallon main tank and 120 Aux tank. The Speedo on the Yami gauge suddenly started working last week and around the same time my Aux fuel gauge went south. It will read correctly for a second or two, then the “bars” will start stepping up until it reads full. Grounds and wiring look good. Haven’t checked the sender yet, but prior owner never used Aux tank, so wondering if that could cause my issue. Any help would be appreciated
 

SkunkBoat

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Grady White Model
Express 265
#2
I have a 265 also.
I have had quirky things with the fuel gauge.

First, I learned you have to wait a long time after switching the readout from Main to Aux or Aux to Main.
When you think you waited long enough...wait some more. Don't toggle back & forth thinking it is not working...that just makes it worse and take longer.

Sometimes it doesn't read anything on AUX even when full, especially when I am filling at the gas dock. Then when I go to try and troubleshoot, its working.
Sometimes I think the float is stuck at the bottom???

Another thing that happened- long confusing story...
I was adding new "Military style(whatever that means?)" terminals to my House battery posts. They are flat and clamp to the big lead posts....I recommend!
This makes the parallel jumpers sit low and frees up space on the threaded posts. Anyway....it was a very sunny day and the battery cubbies are dark and I was wearing dark glasses...
So when I was done everything seemed to be great. Next time out (to gas up) we kept getting low volt alarms on the electronics.. The Fuel gauge would not read correctly in either position.

Back at dock I figured I must have done something to a connection at the battery...always suspect the last thing you did...
My brother is an electrician and had a long piece of #6 wire. We jumped from positive battery to fuse panel in dash..no real change in electronics voltage. Jumped the ground...BINGO! Everything jumped up to 13V and the fuel gauge started working.
So checking connections, the House 6 gauge ground was not on! must have fallen away while I was fumbling with the nut and wrench.
Everything seemed to work until more things were turned on. It was finding a return thru whatever wire it could and thru the fuel sending unit. Since those wires aren't nearly as big as a 6 gauge, the voltage drop was terrible.
Point is, a poor House ground will effect the fuel gauge readings.
 

Harpoon

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#4
Also, on the back of your switch panel check the slide on connectors to the Auk/Main they should be pink wires. Mine slid off recently. You may have a poor connection there.