fuel capacity

FREDSDOG

Cadet
Joined
Jan 22, 2002
Messages
22
i have a 89 larson san marino and i am havinga wierd problemmy gas guage was reading off and ran out of gasihave changed the sender now it seems tobe reading accurately as far as i can tell i have a tank that supposedly holds 80 gal the guage moves 1/8 for every 10 gals up to 3/4 of a tank then i am full with only 60 gal tag on tank says 90 gal capacity i know with boat attitude it effects holding buti do believe it should hold more any thoughts? :confused:
 

Solittle

Fleet Admiral
Joined
Apr 28, 2002
Messages
7,518
Re: fuel capacity

If you bought a "generic" sender rather than the one specified by the tank manufacturer you may either need to calibrate the sender or perhaps the sender that you bought is not the correct one for your tank. Many senders today have a sight guage on the top of the sender itself as well as a connection for the dash guage.
 

Solittle

Fleet Admiral
Joined
Apr 28, 2002
Messages
7,518
Re: fuel capacity

If you bought a "generic" sender rather than the one specified by the tank manufacturer you may either need to calibrate the sender or perhaps the sender that you bought is not the correct one for your tank. Many senders today have a sight guage on the top of the sender itself as well as a connection for the dash guage.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: fuel capacity

Are you saying the tank is actually full or that the gauge says the tank is full. If fuel spits from the tank vent, its full. If the gauge says its full long before the tank is full, you have a very common problem with fuel gauges. They may be accurate at some point on the scale but very few are accurate across the entire scale. Look at it this way. A pyramid shaped tank with a float style gauge would obviously register full when the tank is full. However, only about 1/3 of the fuel is in the upper half of the tank (the narrowest part). When the gauge reads 1/2 you have roughly 2/3 of a tank remaining. The problem here is simply one of linearity. The float rises at a linear rate yet that does not correspond to the shape and volume of the tank. The only solution is to calibrate the gauge for EMPTY as that's the critical point. It doesn't pay to know its accurate when FULL as you know that anyway because you just filled the tank. You want to know when its nearing empty. Adjust the float accordingly or install a fuel flow monitor like the FF41 which provides an accurate measure of fuel used.
 

FREDSDOG

Cadet
Joined
Jan 22, 2002
Messages
22
Re: fuel capacity

i should havebeen more specific the fuel pours out the fill then the vent gauge reads 3/4 replaced with same unit and calibrated filled with an empty tank (ran out) and only took 60 gal when capacity supposed to be 80 tag on tank says 90 gal and guage read full when i first got the boat never thought of seeing actual capacity it makes no sense still scratching my head thanks for your replys
 
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