Got most of the electronics wired but figured I’d show you the gas gauge set up with two tanks and one gauge.
Needed one pull switch that had basically an off, on, on (left & right tanks).
A regular 3 terminal navigation switch won’t work. This 4 terminal did fine.
Don’t depend on the schematic being correct, in my case the bow lights and battery were reversed.
The gauge had terminals for “S” sending unit, “G” ground and “I” ignition or hot and a wire to the dash light bulb.
The “I” terminal is fed from the hot feeding the navigation lights switch.
The “G” terminal goes to the fuse panel ground and the two sending units frame ground.
The “S” terminal goes to the three position switch to the common or in this case labeled “battery”.
The other two terminals on the switch go to the sending units in this case “running lights” for the left tank and “anchor lights“ for the right tank.
The remaining terminal “bow lights” is vacant.
I connected the gauge bulb to the dash light switch but I didn’t connect the navigation lights in the traditional sense by the first position being anchor and the second position being all. What I did was the first position would be all exterior navigation lights and the second position would include the dash lights. This way if the dash lights caused night blindness I could simply exclude them at night. I have a bad habit running at night without lights on so as to be able to see the water.