Just bought a boat with a f115 4 stroke yamaha. The gauge is not showing the right amount of fuel in the tank. When sea trialing it i just thought the level of fuel ( it was reading the bottom bar on the scale and blinking), was because the guy at the marina told me they put in 10 gallons of fuel. It made sense, however, when I went to put ssome fuel in ( 60 gallon tank), I was full at 23 gallons. Now I go up and turn on the gauge and it still reads nearly empty. We then put it on the water and at the dock with the engine running it never moves all day. It also appears that the fuel consumption reading MAY not be functioning properly as well (???). The MPH on the same gauge is working, however. Would it be a bad sender?
2 different components
fuel sender in tank gives you fuel level
paddlewheel sensor in fuel line going to motor gives fuel burn
What’s involved in fixing both problems and how $$$?
Sending units themselves seldom fail, it’s almost always the electrical connections. The sending unit will be on top of the tank somewhere and there should be an access or inspection plate over it. One wire goes to the sending unit, one to ground. Both connections need to be clean and tight. If you short the sender wire to ground the gauge should move.
In the picture below, the round metal disk with the wires attached is the sending unit…
Capt. Larry Teuton
Cracker Built Custom Boats
“Ships are the nearest things to dreams that hands have ever made.” -Robert N. Rose
Had a similar issue early this season. Replaced the sending unit and the gauge didnt work. Replaced the gauge and all is well now. For sure check and clean your connections and tighten down. Then move on to swapping out sending unit then gauge.
No need for the shotgun approach:smiley: If you short the 2 wires on the sending unit together (with the key turned on) and the gauge moves, the gauge and wiring to it is working and sending unit is bad. If the gauge doesn’t move, it or the wiring to it is bad.
Capt. Larry Teuton
Cracker Built Custom Boats
“Ships are the nearest things to dreams that hands have ever made.” -Robert N. Rose
Thanks for the replies. I’ll try the easy fix first.
Update on the problem… I opened up the compartment and the wires running to the sender are both soldered (sp?) onto the top of the cap with a nice rubber cover encasing them. We removed the sender unit from the tank as all the wiring looked to be in factory shape. The sender is a straight metal pole with a dark brown float that runs up and down the shaft of the sender on my boat ( no arm style). We watched the level on the gauge increase and decrease as we moved it up and down by hand. When dipped back in the tank it WILL not float. Don’t really understand this, but it looks like that’s definately the issue and I guess I;ll be seaching the net for a new sender for a 2003 Key West 2020WA with a 60 gallon tank.
It is almost certainly made by Moeller, I think they are available in lengths from about 4" to 18". Just measure the length and find one to match. Many vendors stock them.
Capt. Larry Teuton
Cracker Built Custom Boats
“Ships are the nearest things to dreams that hands have ever made.” -Robert N. Rose
quote:
Originally posted by Cracker LarryIt is almost certainly made by Moeller, I think they are available in lengths from about 4" to 18". Just measure the length and find one to match. Many vendors stock them.
Capt. Larry Teuton
Cracker Built Custom Boats“Ships are the nearest things to dreams that hands have ever made.” -Robert N. Rose
This is what it looks like, but , dang, didn’t measure it before closing it back up…
Looks like some rework is in order… 
Key West 19’6" CC 115hp Merc
14’ Fast Craft w/ 60hp Merc
It appears that “WEMA” has the exact looking sender and I beleive the same screw pattern for $40.00 online. Is this going to work or do I need something from Yamaha?
Whoa, just looked at the Moeller, Larry, and your suggestion looks EXACTLY like it. Thanks, will measure and order one!
No, it doesn’t need to be from Yamaha.
Capt. Larry Teuton
Cracker Built Custom Boats
“Ships are the nearest things to dreams that hands have ever made.” -Robert N. Rose
Yamaha doesn’t even make a sender
its not uncommon that the float becomes saturated and wont “float”
If it were me I would spend the few extra dollars and get the WEMA unit
if you follow the wires up about a foot, you will find a butt connector
replace it and use heat shrink, just don’t use an open flame, use a heat gun
quote:
Originally posted by chris VYamaha doesn’t even make a sender
its not uncommon that the float becomes saturated and wont “float”
If it were me I would spend the few extra dollars and get the WEMA unit
if you follow the wires up about a foot, you will find a butt connector
replace it and use heat shrink, just don’t use an open flame, use a heat gunYeah, I saw the heat wrap and that was my next question. Thanks. I noticed the WEMA senders may be less expensive too. The Key West rep ( Mark Marlowe), told me it’s a 10" WEMA for that boat/tank. Thanks, again for the wealth of knowledge here, boys.
www.teamcharlestonmarine.com
www.joinrfa.org
I take it the sender does not need any calibration? Just install and hook up the wires?
Correct. It’s calibrated for it’s length.
Capt. Larry Teuton
Cracker Built Custom Boats
“Ships are the nearest things to dreams that hands have ever made.” -Robert N. Rose