Gas guage

J

JPsanta

Seaman Apprentice
Joined
Oct 22, 2021
Messages
41
hi , my gas guage was not working in the boat , pulled sending unit and replaced it, hooked it all back up , it reads the gas level now , but when you turn the key off , and shut the battery to off it still reads how much gas in the tank instead of going to zero , looking for help and TY
 
C

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,398
A lot of fuel gauges stop moving when power is removed. When they are powered they move to the correct fuel position. If the fuel tank is empty, they will move to zero when power is applied.

So, if you turn the ign key off, and she has 1/2 tank fuel, and you drain it, the gauge will not move from about the 1/2 position, until you turn the ign key on.
 
K

kd4pbs

Petty Officer 2nd Class
Joined
Mar 5, 2012
Messages
142
Unplug the sending unit when you turn off the boat to ease your mind as to whether or not it is just the way the gauge works.
 
J

JPsanta

Seaman Apprentice
Joined
Oct 22, 2021
Messages
41
i thought it would be like a car fuel guage , went to turn the key off the needle drops to empty
 
S

StewartL

Cadet
Joined
Jul 23, 2025
Messages
27
That's normal for many boats. The gauge often stays on if it has a constant 12V power source from the battery. It will reset when you disconnect the battery or the power is drained. It's not a problem with your new sender.
 
Scott Danforth

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
51,207
gauges should not have constant power. they should be powered by the ignition circuit.

however some gauge air cores do not move to 0 (home) on their own. @JPsanta verify if you have 12 volts on the purple wire on the back of the gauges with the key off.
 
J

JPsanta

Seaman Apprentice
Joined
Oct 22, 2021
Messages
41
interesting , went and checked fuel gauge yesterday at supper time , gauge said tank was full , before when i start this post , i had just under half a tank
 
J

JPsanta

Seaman Apprentice
Joined
Oct 22, 2021
Messages
41
this new sending unit is 33 - 240 ohms , i wounder if there is a compatibility problem with the gauge
 
C

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,398
Depending on fuel gauges to be accurate is tough. My speedboat has been thru 4 or so fuel tank gauges and the equiv fuel gauges changed over the last 45 years. It has a 8" tall tank. So, when the gauge reads empty, there is still 6 gallons left. !/4 tank is 9 gal, full tank is 18 gal. Each new gauge or sender has read the same.
 
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