Fuel gauge question

[Rustygaff]

In the 7 years that I have owned my Freedom, I have always filled my gas tank whenever going to the gas dock. I would then reset the control panel and it would read 135 gallons available. If I partially fill the tank and did a reset, would it read 135 or the partial tank amount? Or if I did nothing, would the gauge recognize the added fuel? I don't want to screw anything up or play guessing games in regards to how much gas I have so I always filled it. Gas prices at our fuel dock are beginning to drop but not sure if its worth the aggravation of guessing how much is in the tank if I do not fill it completely to save a few bucks. When I do fill it, the gauge seems to be right on the money for accuracy. I can guess within a couple of gallons how much it will take when I fill it.

 

[Halfhitch]

When you partially fill the tank, your monitor will have an option for that where you actually enter the number of gallons you added. Be sure you have done your setup, where you can tell the monitor how much fuel can be used from your tank. If you have a full tank and your fuel tank has a capacity of 135 gallons, you do not have 135 gallons available to use. Depending on the configuration of your tank you may easily lack 5 to 10 gallons that will not pickup. So you need to enter the "available gallons" , not tank capacity.

 

[Fishtales]

I fill when I go to the dock. Avoids lines and number of trips - just easier IMHO.

 

[SkunkBoat]

don't confuse the fuel monitoring with the "gauge". The gauge is a float sensor. it reads full,7/8,3/4,5/8, Half,....etc.

the fuel monitor does not sense fuel in the tank. It counts down fuel used by the motor. You told it Full (all tanks) is 135 gallons when you set it up. If you tell it you filled it then it will assume you are starting with 135 gallons. Don't reset to Full if you did not FILL it.

Are you using a Yamaha CL7 (Garmin 7400 clone)? I beleive you can tell it how many gallons you added.

Most MFDs will do the same.

 

[Rustygaff]

don't confuse the fuel monitoring with the "gauge". The gauge is a float sensor. it reads full,7/8,3/4,5/8, Half,....etc.

the fuel monitor does not sense fuel in the tank. It counts down fuel used by the motor. You told it Full (all tanks) is 135 gallons when you set it up. If you tell it you filled it then it will assume you are starting with 135 gallons. Don't reset to Full if you did not FILL it.

Are you using a Yamaha CL7 (Garmin 7400 clone)? I beleive you can tell it how many gallons you added.

Most MFDs will do the same.

Since my boat is a 2011, I believe it is an early version of the 6YC. I believe when the boat was set up, it was programmed for 135 gallons although it holds 150 for a 15 gallon reserve.
Instead of screwing around with it, I think I am going to completely fill the tank as I have done every time in the past because it has worked well. The fuel monitoring system so far has been very accurate.

 

[seasick]

don't confuse the fuel monitoring with the "gauge". The gauge is a float sensor. it reads full,7/8,3/4,5/8, Half,....etc.

the fuel monitor does not sense fuel in the tank. It counts down fuel used by the motor. You told it Full (all tanks) is 135 gallons when you set it up. If you tell it you filled it then it will assume you are starting with 135 gallons. Don't reset to Full if you did not FILL it.

Are you using a Yamaha CL7 (Garmin 7400 clone)? I beleive you can tell it how many gallons you added.

Most MFDs will do the same.

Skunkboat: I know that swing arm type senders change resistance in 'infinite' steps. That is to say that the output is a continuously changing resistance as the arm is swung. What I don't know is if the KUS (WEMA) style rod senders have stepped output resistances for specific levels as you allude to. The KUS site doesn't clarify. I don't have a sender handy to check and to be honest, it never occurred to me that the output might be incremental changes in resistance.

 

[SkunkBoat]

Its a moot point if you have a digital gauge that only has 8 segments.

Honestly I don't know the resolution of the KUS senders. It may be more than 8 steps.
Even the older sensors are at the mercy of the resolution of the A/D conversion

My point was that "gauges" don't read gallons they read a level.

 

[seasick]

All valid points. I was just wondering if when using an ohm meter to check for problems, the changes would be continuous or incremental. With the swing arm types, 'intermittent' or dead spots are possible. Can that happen with the rod type senders?
In other words could you have a bad sender that can read 1/2 tank, then empty, then 3/4 as you fill the tank?

 

[Hookup1]

The WEMA stainless tubes contain a series of magnetic reed switches and resistors. The magnetic donut slides, trips the reed switch and changes the resistance. A bad reed switch or resistor will give you incorrect readings. You have to pull the sending unit to test. Sending unit can not be repaired - replace it. They come in different lengths so make sure you get the same one.

 

[SkunkBoat]

All valid points. I was just wondering if when using an ohm meter to check for problems, the changes would be continuous or incremental. With the swing arm types, 'intermittent' or dead spots are possible. Can that happen with the rod type senders?
In other words could you have a bad sender that can read 1/2 tank, then empty, then 3/4 as you fill the tank?

Hookups decsription is correct. They are in series so going from 1/2 to empty to 3/4 is not going to happen.

 

[Hookup1]

Hookups decsription is correct. They are in series so going from 1/2 to empty to 3/4 is not going to happen.

I’m not sure about that. If the 5/8 reed switch fails it will go to empty.

There are eight 30 ohm resistors in series with a reed switch at each junction. The other side of the reed switches are combined together and connected to the common. As the magnet slides up/down a reed switch will close and you will have 1 to 8 resistors in the circuit. If you have a bad reed switch you would have an open or a empty tank. If a resistor is open you will read empty below that point.

 

[seasick]

I’m not sure about that. If the 5/8 reed switch fails it will go to empty.

There are eight 30 ohm resistors in series with a reed switch at each junction. The other side of the reed switches are combined together and connected to the common. As the magnet slides up/down a reed switch will close and you will have 1 to 8 resistors in the circuit. If you have a bad reed switch you would have an open or a empty tank. If a resistor is open you will read empty below that point.

View attachment 26341

Good sketch.
Thanks

 

[SkunkBoat]

I’m not sure about that. If the 5/8 reed switch fails it will go to empty.

There are eight 30 ohm resistors in series with a reed switch at each junction. The other side of the reed switches are combined together and connected to the common. As the magnet slides up/down a reed switch will close and you will have 1 to 8 resistors in the circuit. If you have a bad reed switch you would have an open or a empty tank. If a resistor is open you will read empty below that point.

View attachment 26341

yes thats what I said.
it won't "read 1/2 tank, then empty, then 3/4 as you fill the tank"

I am pretty sure they "make before break" so you don't drop to empty between steps

 

[Hookup1]

yes thats what I said.
it won't "read 1/2 tank, then empty, then 3/4 as you fill the tank"

I am pretty sure they "make before break" so you don't drop to empty between steps

One change to my diagram. replace the bottom (empty) reed switch with a wire. Normal 240 ohm state is empty.

I'll bet as the magnet slides it does as you said "make before break". It's likely that two reed switches could be closed at any given time. This isn't a problem because the correct resistor is connected to ground and you get the correct resistance.

But if the magnet is positioned over the bad "open" 1/2 tanks reed switch it may be possible to get an "empty" reading.

How many angels did we count on that pin head?

 

[seasick]

Many angels.. The 'devil' is in the details

 

[sturgstev]

Had to do a repower our 2004 GW228 with a Suzuki 250 along with the c-10 gauge.

The fuel management system is impossible to use due to lack of fuel docks in my area. Have to add fuel with five gallon jugs. Boat is at a marina.

Just wondering if the fuel tank has a floating system that a standard fuel gauge would be available to install.

Many thanks

steve

 

[SkunkBoat]

If they did not replace the existing Grady oem fuel sensor then you could certainly connect it to an analog gauge.

What year suzuki? Why the C10 gauge and not the newer SMG4?

I think the C10 might require a NMEA2K level sensor (like a KUS NS5) to display fuel level.
If you have that you can get a calibrated very accurate fuel level reading on the C10

I don't remember if it will display a fuel level from an analog fuel sender unit

Your C10 should receive fuel burn data from your motor.
You should be able to set the C10 to know your tank capacity. You should be able to tell it you have filled the tank or added 5 gallons...
Once you accurately tell it how much you are starting with the C10 should be able to display gallons USED.

The C10 is a rebranded Simrad MFD I think.
The SMG4 gauge is much better. It is a Suzuki dedicated display/gauge. It will connect to old-school fuel sensors (2 of them).

 

[sturgstev]

The Suzuki was purchased about four years ago.

When i get the boat serviced again at the end of 2022 I will ask them to install a analog gauge.

Here we have to add gas at 18 gallons at a time with four five gallon jugs.

I just put in 36 gallons and the c-10 read 92 gallons before the last four gallons was added.

thnx

steve

 

[Chessie246G]

If they did not replace the existing Grady oem fuel sensor then you could certainly connect it to an analog gauge.

What year suzuki? Why the C10 gauge and not the newer SMG4?

I think the C10 might require a NMEA2K level sensor (like a KUS NS5) to display fuel level.
If you have that you can get a calibrated very accurate fuel level reading on the C10

I don't remember if it will display a fuel level from an analog fuel sender unit

Your C10 should receive fuel burn data from your motor.
You should be able to set the C10 to know your tank capacity. You should be able to tell it you have filled the tank or added 5 gallons...
Once you accurately tell it how much you are starting with the C10 should be able to display gallons USED.

The C10 is a rebranded Simrad MFD I think.
The SMG4 gauge is much better. It is a Suzuki dedicated display/gauge. It will connect to old-school fuel sensors (2 of them).

Excuse my limited knowledge, but I think they make an adaptor to connect a a non Nmea sender to a Nmea network. 2 wires with some sort of electrical box to Nmea connector.
My old boat and my old self is just learning about Nmea2000 networks. Need to upgrade the Grady to get accurate fuel readings/burn. Much cheaper to convert to Nema then buy the old Yamaha sensors and gauges.

 

[SkunkBoat]

Excuse my limited knowledge, but I think they make an adaptor to connect a a non Nmea sender to a Nmea network. 2 wires with some sort of electrical box to Nmea connector.
My old boat and my old self is just learning about Nmea2000 networks. Need to upgrade the Grady to get accurate fuel readings/burn. Much cheaper to convert to Nema then buy the old Yamaha sensors and gauges.

Yep, the Simrad/Lowrance/Garmin/Raymarine brands used to cost as much as an N2k sensor dunno what they go for now