Fuel selector question

[Jrspawn]

So on my 01 Grady marlin, I am trying to figure out which outboard(port or starboard) each of the fuel selector valve actually goes to. Right now each outboard runs off of a separate tank, one on the main and one on the aux. I’m just not positive which tank is feeding which outboard. I’ve also noticed that the fuel gauge reads quite a bit lower when the switch for aux tank is on. I never really fill it to the brim when fueling it up so it’s hard to verify if it’s actually lower or if it’s the sender/gauge? Has anyone ever ran into this before? Thank you!

 

[Jrspawn]

Mine are as pictured.

 

[SkunkBoat]

I would assume the one to port is the port motor and the one to starboard is the starboard motor.
Of course, someone could have f'd it up.
You can test by turning one to off and see which motor runs out of gas. Or follow the center hose to the motor.

The short pointy end of the handle points to the tank you are using.


The position of the fuel valve has no relation to the reading on the gauge.

You said "when the switch for aux tank is on". Do you mean the electrical switch on the dash that chooses which tank is displayed?
That is unrelated to the first question?

 

[Jrspawn]

I would assume the one to port is the port motor and the one to starboard is the starboard motor.
Of course, someone could have f'd it up.
You can test by turning one to off and see which motor runs out of gas. Or follow the center hose to the motor.

The short pointy end of the handle points to the tank you are using.


The position of the fuel valve has no relation to the reading on the gauge.

You said "when the switch for aux tank is on". Do you mean the electrical switch on the dash that chooses which tank is displayed?
That is unrelated to the first question?

Yes, the switch on the dash that switches fuel tanks for displaying fuel levels.

 

[SkunkBoat]

So you think that it does not reflect the correct % of volume? It never shows full or shows full when its not?

There is a lot of error in sender/gauges. They are rarely precise. There are float/arm types that can be mis-adjusted. Even the newer Hall effect senders are only as accurate as the length from bottom to top. The dead space below or above the sensor is lost. V bottom tanks are not linear.

Idk about a Marlin but often the Aux tank is smaller than the Main. So if you are going by the GALLONS you put in compared to the Main tank then a half tank is fewer gallons.

The best way to know how much fuel is in each tank is to FILL them, reset your fuel monitor(if you have that)for "top off tanks" and run both motors on one tank. Your fuel burn will be from that tank and the other will be full.