Need a SmartCraft Gauge expert

[Timsjag]

I have two 2008 SmartCraft 1000 gauges on my boat (repowered 1995 Islander 26.8). The repower was a 2008 Merc Verado 300. It came with two SmartCraft 1000 gauge. When I got the boat back from the boatyard they did not hook up the fuel sensing unit to the gauge (seems they had the wrong harness). Anyway I've worked through that but on a full tank (134 gal) the gauge reads 96 gallons (the gage was calibrated to 134 gallons for full tank) I've run it a while (burned about 25 gallons) and the gauge now read 86 gallons. I've looked at all of the literature and can not find anywhere where you'd calibrate the fuel sensing unit to the gauge (the fuel sense unit is measure in ohms). Does anyone with knowledge of smartcraft gauges know "IF" there is a calibration setting for the fuel sensing unit? Or do I need to replace my fuel sensing unit (it's most likely 25 year old.

Thanks

 

[seasick]

There are Speedometer config settings for tank calibration. I think it is under the heading External Sensors in the CAL 2 menus ( It might be CAL 1)
You have to make sure you set the sensor as fuel tank of course. Then you need to select the option to calibrate ( as opposed to SKIP option).
You then have two fuel tank options: On where you start with an empty tank, set the gauge, add a quarter tank of gas, calibrate the 1/4 level. do the same for 1/2 3/4 and full. You also need to enter the tank capacity when prompted
The second option which is less accurate and maybe a lot less accurate depending on the tank shape is to just assume that the low sensor reading is empty and the other levels are proportional to the level of the sender float (same concept for WEMA type senders.)
There are several web sites that have the instructions for Smartcraft gauges.
First thing to do is make sure you know how to display the current settings and write them down.
The second is to NEVER, NEVER do a master reset.