25 U.S. Gallons, but where?

[0TreeLemur]

There is a tab inside the fuel tank near the inlet on our J.  It says 25 US GALS, but there is no level datum marked.   Where is the 25 gallon level on this tab?  The POH doesn't say.  Is it at the flat portion at the bottom of the tab below the small hole or at the bottom of the big oval-shaped holes?  Photo:

 

[1980Mooney]

14 minutes ago, 0TreeLemur said:

There is a tab inside the fuel tank near the inlet on our J.  It says 25 US GALS, but there is no level datum marked.   Where is the 25 gallon level on this tab?  The POH doesn't say.  Is it at the flat portion at the bottom of the tab below the small hole or at the bottom of the big oval-shaped holes?  Photo:

 

Fill to the bottom of the tab. 

 

[N201MKTurbo]

I find when I'm filling the tank, if I fill it till the swirling fuel gets to the little hole, it will settle to the bottom of the tab after I turn off the nozzle.

[0TreeLemur]

While at hangar today, I notice that the right tank in-wing sight gage said 25 gallons.  Opened it up and took this photo.  Seems right on.

 

[PT20J]

1 hour ago, 0TreeLemur said:

While at hangar today, I notice that the right tank in-wing sight gage said 25 gallons.  Opened it up and took this photo.  Seems right on.

 

Mine, too. I always wondered what that hole was for. I wonder if that's where the the fuel cap lanyard (removed by AD for hanging up the fuel level float) used to attach. Anyone know for sure?

[N201MKTurbo]

22 hours ago, PT20J said:

Mine, too. I always wondered what that hole was for. I wonder if that's where the the fuel cap lanyard (removed by AD for hanging up the fuel level float) used to attach. Anyone know for sure?

As I mentioned in another thread, it would be cool to make a permanent aluminum dip stick with gallon marks and bolt it to the back of the tab using that hole. Sure you will cuss and swear working the hardware, but it’s a Mooney after all. You can retrieve all the dropped hardware with your magnet. 
 

If you riveted a nut plate to the dipstick part, it might be doable.

[Igor_U]

I asked this question myself and believe 25 gals is when fuel is touching tip of the tab however, I'm sure someone posted it's at the bottom of the hole. 

I checked again last night and my calibrated fuel stick (made out of HD paint stick) shows 25 gal at the bottom (tip0 of the metal tab, not the hole. 

[carusoam]

Expect the hole… is the calibrated mark…

It would be unusual to include the settling in the measurement… it is most likely a random event that it settled to the bottom of the tab…(?)

This should be documented in the plane’s POH… if it has a paragraph on service, filling the plane…

PP thoughts only, not a mechanic…

Best regards,

-a-