Fuel level measurement

H

hjbutler

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Location
Lake Texoma
Model
Adventure
Hello everyone!

I have a 1994 Adventure and I'm wondering if there is a good way to physically check the amount of fuel in the tank. Recently the fuel gauge failed to work and I fixed it by cleaning and reattaching the wires on the tank. After this fix, the level read 1/4 tank higher than it did before it failed. This makes sense, with more current getting through to the gauge. However, it has left me with little confidence in the accuracy of the gauge. Furthermore, the gauges are all new Suzuki following repower last year. Any suggestions? I'd like to achieve some confirmation of what's actually in the tank.
 
The other alternative is to simply use the motor computer to tell you fuel consumed. The fuel gauges on my boat are off, the fuel consumed is much more accurate anyway, and I also keep a running table in the notes app on my phone. Logs date, gals added, gals burned, and remaining fuel. This has been more than good enough for me. I do need to remember to reset the fuel used gauge after each time adding fuel - that number is the fuel burned in the table.
 
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With the boat level, you can remove the fuel sender and simply "dip" the tank to physically check the level as you asked.

If it's a square bottom tank, you can easily do a simple calculation based on the size/volume.
 
The bottom of the 208 is rarely level and changes if you go aft ( 3 or 4 feet,) The fuel level at the sender can change a lot as the boat's pitch changes.
Motoring with the bow up will give a gas reading that can change by 10 gallons or more when the bow drops.
Likewise a pitched up bow can display an overly optimistic reading as the gas will pool towards the back of the tank.
If you rely on the fuel gauge for accurate levels you will eventually run out of gas at sea:)
Fuel flow rate and usage if provided by your engine is way more accurate than a gauge.
 
seasick said:
If you rely on the fuel gauge for accurate levels you will eventually run out of gas at sea
Click to expand...
Holy crap! I bought my first boat in 1962 and have been using a fuel gauge all this time and have never run out of fuel at sea! I must be running on borrowed time. That settles it, I ain't going out there again!
 
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Make sure the zuke is set to american vs euro gauge.
Swing arm fuel senders are not accurate. Hall effect senders are better but they are divided into 8 levels. Thats the BEST they can do. Your tank have a v bottom then the bottom 1/8ths hold less than the top 1/8ths. Then there is the levelness of the tank. and then there is the levelness of the tank when you were filling (which effects when it overflows as FULL) vs when you are running/floating. If you fill on a trailer or in the water and how many people were leaning on that side while you pumped.

Fill tank. Reset Trip before you do anything else.
Use the fuel burn on the zuke gauge. It will tell you how much you have used since FULL. Assume "FULL" can be 5 gallons short.
 
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Halfhitch said:
Holy crap! I bought my first boat in 1962 and have been using a fuel gauge all this time and have never run out of fuel at sea! I must be running on borrowed time. That settles it, I ain't going out there again!
Click to expand...
:

You are the exception but we already knew that :)
 
Halfhitch said:
The best way to go for accuracy/dependability is to purchase sending units from KUS. They, along with your new gauges will relieve the stress level for you when you need to know for sure. They are available from many vendors.
https://kus-usa.com/product/sss-ssl-sender/
Click to expand...
Thanks for the idea. I noticed that they have specific Ohm readings for levels. I may put a meter on the sender and see if the Ohm reading jibes with the gauge level. Might be interesting.
 
kirk a said:
The other alternative is to simply use the motor computer to tell you fuel consumed. The fuel gauges on my boat are off, the fuel consumed is much more accurate anyway, and I also keep a running table in the notes app on my phone. Logs date, gals added, gals burned, and remaining fuel. This has been more than good enough for me. I do need to remember to reset the fuel used gauge after each time adding fuel - that number is the fuel burned in the table.
Click to expand...
My engine does not have a computer.
 
DennisG01 said:
With the boat level, you can remove the fuel sender and simply "dip" the tank to physically check the level as you asked.

If it's a square bottom tank, you can easily do a simple calculation based on the size/volume.
Click to expand...
DennisG01 said:
With the boat level, you can remove the fuel sender and simply "dip" the tank to physically check the level as you asked.

If it's a square bottom tank, you can easily do a simple calculation based on the size/volume.
Click to expand...
I am going to do this. That will at least give me a "real world" reference.
 
seasick said:
The bottom of the 208 is rarely level and changes if you go aft ( 3 or 4 feet,) The fuel level at the sender can change a lot as the boat's pitch changes.
Motoring with the bow up will give a gas reading that can change by 10 gallons or more when the bow drops.
Likewise a pitched up bow can display an overly optimistic reading as the gas will pool towards the back of the tank.
If you rely on the fuel gauge for accurate levels you will eventually run out of gas at sea:)
Fuel flow rate and usage if provided by your engine is way more accurate than a gauge.
Click to expand...
Yes, I'm well aware that it shows more fuel when the boat is bow up.
 
Halfhitch said:
Holy crap! I bought my first boat in 1962 and have been using a fuel gauge all this time and have never run out of fuel at sea! I must be running on borrowed time. That settles it, I ain't going out there again!
Click to expand...
LOL. Same here. But I never let it go below 1/4 tank.
 
I would expect that your new Suzuki motors track fuel burn. Your gauges may not report fuel burn. But newer chartplotter can be interfaced to the engine to report it.

Also the old fuel sending units in the tank(s) should be replaced with KUS WEMA sending units. You need to know the proper length (tank depth). Easy swap but don't pull the sender out with a full tank - 1/2 tank would be best.

Fuel level in a boat with sending units is never going to be accurate. Too many things going on. At best it will give you an idea of where you are on fuel. I know when my tank is full and if if I'm below 2/8's of a tank I'm very careful. If you are running around with 1/8 tank you could run out of fuel simply by just coming off of plane into a "no wake" zone.

The engine fuel burn from the motor (gauges or chartplotter) is very accurate. But you still have to deal with the boats ability to get the last drop out of the tank.

My advice and what I do on my boat is to have both the boat fuel gauge with a working sending unit and my chartplotter interfaced with engine fuel consumption.
 
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