another fuel gauge question

sidewalkman

Cadet
Joined
Sep 8, 2014
Messages
13
My fuel gauge sort of works, but seems like it is sticking. Is it as simple as removing the float system from the tank and inspecting and maybe cleaning the sender? I've done it dozens of times on motorcycles.
 

NHGuy

Captain
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May 21, 2009
Messages
3,631
Yup, but be cognizant of fuel vapors 'cause they collect in the bilge. Disconnect the battery before you start.
You can take out the sender and test it with an ohmmeter. In boats they wear out from the constant movement, so replacing is common.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Fuel gauges are the combination of a floating bulb in the tank varying the resistance of a wire wound resistor, therein, in series with a meter movement, across 12v-gnd. Problems with senders are not uncommon as the sloshing of the fuel causes the wiper of the variable resistor in the tank to rub over and over the wire of the resistor part. After awhile one or the other craters. If you keep a relatively constant fuel level it may be the resistor wire wear into, but usually, it's the wiper attached to the float that gets it's contact worn off. Common problem due to age and agitation. Since the float is a mechanical device and not lubricated with any sort of oil, it could stick, or the wiper could stick on the resistor as a result of constant agitation. Least likely is a sticking meter but is possible.

Mark
 

sidewalkman

Cadet
Joined
Sep 8, 2014
Messages
13
Thanks, the boat is a '90 so likely a new sender is in order. I'll pull it over the winter and see if I can find a replacement!
 

UncleWillie

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Oct 18, 2011
Messages
3,995
Newer boats have the newer style senders.
They are a floating magnet ring surrounding a tube with 8 magnets switches inside.
The sender will only indicate 8 positions, and they tend to not be evenly spaced.
Is is possible for the gage to jump form 1/2 to 3/4 instantly with nothing in between.

Also a tank with the sender in the rear and the bow of the boat in the air can read FULL on the gage until more than half the tank is gone.
It will appear to be stuck on Full for a long time and then quickly swing down to empty.

Boat fuel gages are notoriously inaccurate for multiple reasons.
Are you sure there is really a malfunction?
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Another thing is adjustment. Most are adjustable and the reason is to accommodate a single sender to multiple dimensioned tanks. You adjust it to fit your needs and ensure that you have allowed enough room for it to move the full length from full to empty. Then think about what kind of reserve you want. When the gauge reads E, how far is it to the boat dock or the marina? Set it for that.

Mark
 

sidewalkman

Cadet
Joined
Sep 8, 2014
Messages
13
Newer boats have the newer style senders.
They are a floating magnet ring surrounding a tube with 8 magnets switches inside.
The sender will only indicate 8 positions, and they tend to not be evenly spaced.
Is is possible for the gage to jump form 1/2 to 3/4 instantly with nothing in between.

Also a tank with the sender in the rear and the bow of the boat in the air can read FULL on the gage until more than half the tank is gone.
It will appear to be stuck on Full for a long time and then quickly swing down to empty.

Boat fuel gages are notoriously inaccurate for multiple reasons.
Are you sure there is really a malfunction?

Riding on plane, or stopped it reads full, but moves when I turn on the boat, then if a hit a wave or jolt the boat it will give me an accurate reading until I shut it down and later restart, then again full.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Where is your fuel gauge when the ignition switch is off? Stuck where it was when you turned the key off or at F or E? If at F or E, that is the meter position when no current is flowing in the circuit like would happen with a worn out wiper that can't connect to the resistance winding and tells you your resistor is open ckt. Or bouncing around causes the gas to slosh which makes the float move up and down which runs the wiper up and down the resistor and as such moves across the open circuit, makes good contact, gets some current through the circuit and you get a decent reading. Not rocket science. You are on the right track. When your tank equipment comes in, install it and be on your way.

Mark
 
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