Tank-R

[Hawkeye]

My 1961 M20b has a switch market "Tank-R" above it.  If I switch it down, does the gauge then read Total fuel remaining or Left tank?

When down, does the meter read Right & Left tanks together?  Is Tank-R so that Tank-R minus Total = Left Tank?

[Piloto]

TANK-R switch could be to enable a reserve tank fuel pump. Look in the baggage area and others for an extra fuel tank.

José

[Hawkeye]

No reserve tank.  Two 27.5 gal bladder wing tanks.

[FoxMike]

A way to figure out what the gauge is telling you, fill the tanks and fly for an hour or so.  Use the left tank.  After an hour the plane should have burned at least 7 gals. probably a little more.  If the gauge reads 3/4 you are seeing the quantity in the left tank.  If the gauge reads about 7/8 you are seeing the quantity in both tanks.  Put the switch in the right position and you should see a the gauge showing full.  You might want to fly a little longer so the differential is greater.  I would guess that the gauge is reading total fuel quantity in both tanks except when you hold the switch in the right position.  This is an important question that needs an accurate answer.  Good Luck!

[carusoam]

Mooneys typically have two independent gauges for fuel level.  One left and the other right.

By the picture you are showing, it seems to me that you have one gauge. The switch is probably the only method to read the two tanks using one gauge.

Somebody has gone and made changes to your electrical system.  They have added an alternator and a radio switch.  And the switch layout doesn't match my memory of what was in my C.

See if they have updated the wiring diagram in the POH to match your panel.

Best regards,

-a-