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Fuel Sender Index Fix: Read if your fuel gauge never quite goes to full or empty.

Luc Lafreniere

Jetboaters Captain
Staff member
Scarab Forum Lead
Messages
1,454
Reaction score
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Points
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Location
Ottawa, Canada
Boat Make
Scarab
Year
2015
Boat Model
165 G
Boat Length
16
This keeps happening to owners. I decided to post it here since I just responded to someone on Facebook. Hopefully it proves useful in the future. If you are uncomfortable with fuel... then please seek help from a pro. Use your dealers, etc. But if that's not an option or you're comfortable dealing with a fuel tanks, here are the details.

1. Find the top of your tank. On a 165 for example, it's under the middle seat under a white cover with 6 screws. You pop off the seat, remove the 6 screws and you'll see what's in this pic. Not sure where yours is located on your boat, but most likely somewhere in the middle of the boat.

2. Note the shape of the tank. The tank has internal walls, cutouts, etc. The fuel sender has a float (like a toilet) that is fixed inside. The position of this float is important since it's on an arm that is fairly long. If it's not oriented correctly, the float will contact one of those tank walls and stop going up. Which is your problem. The red line drawn shows the CURRENT position of the fuel float relative to the sender position. Not that it's 90 deg CCW from the electrical connector. Easy to remember that way. Have a look at yours and you'll discover your float is probably too close to one of those tank walls.

3. To fix, make sure you're battery is completely disconnected. No source of sparks, etc. I recommend you disconnect the electrical connector (just a little tab/button to push and wiggle the connector loose carefully). Leave the fuel line connected. IF you decide it's in the way, make sure to clamp it before doing so otherwise a bunch of fuel will come out of the line. Also have rags near by to catch any little fuel spillage. Nothing will come out of the tank, but it will come out of the fuel line. If clamped, very little. It's once again, a little tab/button and you wiggle it loose.

4. The fuel sender is under constant pressure UPward because of two springs inside. That means it keeps pushing against the large, plastic nut (blue in the pic). Your job, should you choose to accept it, is to maintain a constant DOWNward pressure on the fuel sender with your thumbs while SIMULTANEOUSLY unscrew the large, plastic nut. This is the hard part. It's on there VERY tight. They make a special tool to unscrew it, but it's possible to unscrew by hand with brute force. But you need a LOT of strength and your fingers will hurt. The first time I did it, I used a large flat head screwdriver and a hammer and slowly tapped against one of those little tabs until it got loose. I recommend having someone else keep pressure on the sender if you do this. Also, if you're not careful (don't ask how I know), you can break one of those plastic tabs. So DELICATELY do this if you do. As soon as it starts moving a bit, you really need to switch to hands otherwise you risk breaking those tabs. It will still work just fine, but losing those tabs makes it a lot hard to tighten/loosen.

5. Do NOT unscrew it entirely, you just need to loosen the nut so that you can rotate the sender. Once loose enough, you can grab onto the connector and fuel line area and easily rotate with minimal pressure (no risk of breaking those). Keep some small pressure downward so it's easy to spin. Those springs will constantly work against you.

6. Rotate to the correct position for your scenario. That all depends on your current float location. Use my image to note where it needs to go. Make sure the float will move freely. Be careful not to rotate past one of those tank walls because you'll break it. Usually, it's close and just needs a 5-10 deg movement to fix. CW or CCW, depends on where it is now.

7. Re-tighten the large plastic nut while keeping constant downward pressure. Make sure it's very snug so there's no fumes that come out. Re-attached the electrical connector (and the fuel line if you disconnected it) and put the cover back on.

Note: It really is like a toilet float on a relatively delicate arm. Please be careful when handling all of this. Also note that depending on where you position your float, it will affect your fuel level somewhat. So for example, if you position it farther toward the stern, then when you accelerate, it will read more fuel, toward the front, opposite. Etc. You have to note that ALL boats have a fairly inaccurate fuel gauge. They are not perfect and gas moves around all over while boating. You have to keep that in mind whenever using a boat fuel gauge. Also, if the nut wasn't installed tightly enough, vibrations can cause the sender to rotate again. So it's important to make sure it's TIGHT. Could be the manufacturer installed it correctly but didn't quite tighten it enough.... so over time, it moves. But if it's from new, then something wasn't quite positioned correctly. An easy fix obviously.

Hopefully this all helps and you can fix it yourselves.
 

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