Ultrasonic fuel sending unit

[Ethan's Tank]

My fuel gauge isn't working and I noticed in the searay schematic, it mentions an ultrasonic fuel sending unit. I didn't unscrew the 5 bolts, but there a black cap on the top of the fuel unit. Does anyone know how to mess with this type? I'm not sure if this is a traditional type since I've never seen it before. Looks like a skinny circuit board encased in a plastic sleeve.

 

[Express 390]

My fuel gauge isn't working and I noticed in the searay schematic, it mentions an ultrasonic fuel sending unit. I didn't unscrew the 5 bolts, but there a black cap on the top of the fuel unit. Does anyone know how to mess with this type? I'm not sure if this is a traditional type since I've never seen it before. Looks like a skinny circuit board encased in a plastic sleeve. View attachment 89119 View attachment 89119 View attachment 89122 View attachment 89123 View attachment 89124

I have to say thats a first for me too i never seen one like that either !

 

[stephens013]

I just wish I could even get to my fuel sending unit

 

[Ethan's Tank]

I just wish I could even get to my fuel sending unit

What kind of boat you got

 

[hughespat57]

That style does not look like an ultrasonic, an ultrasonic is like a depth sounder, just a puck at the top of the tank and bounces sound off the top of the fuel.
What you have should be magnetic float around an aluminum or stainless tube, which can break or stick
The circuit board is a series of reed switches and resistors, as the magnet floats up it triggers a different switch and resistance

If you can get the board out that easy take a small magnet and slowly move up from the bottom and the gauge should follow

 

[stephens013]

2001 510DA. Main center tank sending unit is under a floor that was installed over the access hatch. Ain't about to tear out the floor. Just fill her up and add up the run time.

 

[Ethan's Tank]

That style does not look like an ultrasonic, an ultrasonic is like a depth sounder, just a puck at the top of the tank and bounces sound off the top of the fuel.
What you have should be magnetic float around an aluminum or stainless tube, which can break or stick
The circuit board is a series of reed switches and resistors, as the magnet floats up it triggers a different switch and resistance

If you can get the board out that easy take a small magnet and slowly move up from the bottom and the gauge should follow

Thank you for that explanation, I will try your magnet idea tomorrow.
Now the big question, since there is a searay dealer close-by to me, is there a special part name for this? I called them today, they looked up my HIN and told me to use a universal moeller mechanical float switch. I'm wondering if searay stop doing this style or if I can order the part from an online site.

 

[Ethan's Tank]

I found them at west marine and Amazon, thanks a lot...if this fixes my issue, then next thing is the 240degree engines problem

 

[ttmott]

Those little black things are reed switches and the resistors change the resistance as each reed switch opens and closes. There is a stainless tube that slides into and a magnetic float that slides up and down the outside of the stainless tube. The magnet closes the reed switches as it slides up and down. That inner part should never have been able to be removed.
A direct replacement is made by KUS - many of us have changed to these including myself. Measure the length and order direct.
https://kus-usa.com/product/sss-ssl-sender/

 

[hughespat57]

Before replacing follow the black cable to some butt connectors
Two should go to the cable
If it originally had ultrasonic there may be third taped off that would be 12v+ from the ignition used to power the ultrasonic electronics
One is ground
One is the gauge
Short the gauge to the ground
Fuel gauge should go to bottom
Open circuit gauge should go full scale
If not the gauge or wiring is bad
https://www.sailmagazine.com/diy/test-replace-fuel-gauge-sending-unit

 

[Ethan's Tank]

Before replacing follow the black cable to some butt connectors
Two should go to the cable
If it originally had ultrasonic there may be third taped off that would be 12v+ from the ignition used to power the ultrasonic electronics
One is ground
One is the gauge
Short the gauge to the ground
Fuel gauge should go to bottom
Open circuit gauge should go full scale
If not the gauge or wiring is bad
https://www.sailmagazine.com/diy/test-replace-fuel-gauge-sending-unit

On the wiring harness, the butt connectors are black, pink, purple.
Purple is cut for some reason. It's the same on port and starboard side
I have to get under the helm to look at wiring for the gauge, but decided on the sending unit since I have medical issues preventing me from twisting my body and squeezing under there right now



View attachment 89137

 

[Keith Zibilich]

My fuel gauge isn't working and I noticed in the searay schematic, it mentions an ultrasonic fuel sending unit. I didn't unscrew the 5 bolts, but there a black cap on the top of the fuel unit. Does anyone know how to mess with this type? I'm not sure if this is a traditional type since I've never seen it before. Looks like a skinny circuit board encased in a plastic sleeve. View attachment 89119 View attachment 89119 View attachment 89122 View attachment 89123 View attachment 89124

I had an issue with my fuel gages being inaccurate and contacted Sea Ray to find out who manufactured the fuel tanks. In my case it was Florida Marine Tanks (Phone: 305-620-9030) so, I contacted them and they were very helpful. The ultrasonic sending unit that was installed was no longer manufactured and they recommended and sold me the new replacement sensor for my boat. I installed the new Wema KUS 32" unit in about 30 minutes and both gages are now very accurate.

In your case, it may simply be a wire connection that can easily be tracked down with a multimeter.

 

[Ethan's Tank]

Magnet floats, Reed switch is working with gauge, so not sure what the issue is. I will reinstall and see if it works now. No one has in hand, except mechanical arm type and Sea trial is tomorrow. FML.
I may have to go back to old style so buyer can take it home. Searay dealer told me they abandoned this style years ago anyways