Fuel Tank gage issues

[Major Woods]

Have 2004 GW Marlin 300.
Long trip this weekend, ran the main tank down till the fuel gage stated flashing on the last bar (Warning Empty), switched tanks and kept on going.
When back at the marina, filled the tank up and it only took 115 gallons.

The owners manual says its a 150 gallon tank, is the fuel gage not being even close to accurate a normal situation?
Is there a fix, put in aftermarket sender unit?

Thanks

 

[Hookup1]

My fuel tank gauge is reasonably accurate. When it starts flashing the tank is very low. Gauges are affected by the attitude of the boat. If you are bow high all the fuel runs to the back of the tank and will give you higher readings. When you come off plane and level out (you might even go slightly bow down) and run out of fuel (pickups aft in tank). Gauges are a guide - not the same as your car!

That said you can test your sending unit (ohm meter slide pickup). If sending unit was replaced they may have put the wrong length on in.

Or just replace it with a WEMA style sender (I did both of mine). Make sure your tank is down about a 1/4 tank before pulling the sender. Sender is clocked and will only bolt in one way for screws to line up. Use a new gasket. Permatex fuel-safe gasket prep if the tank is badly corroded around sending unit.

 

[trapper]

Hookup1 do you know what is left in the tank in gallons or litres when the Yamaha gauge starts flashing?

 

[Neeen]

I would be curious too - actually just had this happen, ran the tanks down to one bar flashing (at dock, not moving). yamaha electronic trip gauge shows 178gals used. the fuel tank spec says the tank holds 230gal. This would leave 50gals reserve at flashing one level bar. I filled the tank and it did take 178 gals. and I know it is full. anyone else have matching numbers?

 

[seasick]

Have 2004 GW Marlin 300.
Long trip this weekend, ran the main tank down till the fuel gage stated flashing on the last bar (Warning Empty), switched tanks and kept on going.
When back at the marina, filled the tank up and it only took 115 gallons.

The owners manual says its a 150 gallon tank, is the fuel gage not being even close to accurate a normal situation?
Is there a fix, put in aftermarket sender unit?

Thanks

By the very nature of boats and hull angles, the gauge is not as precise as folks think.
Just by walking around the deck can change the angle of the tank and that will skew the reading. If everything was level and not moving, the flashing bar , when it starts flashing does not mean the tank is empty, it indicates that an eighth or less of the range of the sender.
Depending on the type of sender, KUS style linear or old fashion swing float, that reading can mean a decent range of gas quantities. In addition, the sender itself sits above the tank bottom, so that empty to the sender is not actually an empty tank. Note that the flashing bar can represent an eigth or so or zero ( and there is still gas in the tank below the sender.
The bottom line is that if you rely on the sender information to accurately tell you how much gas you have, you will someday run out of gas
On my boat I can get a more accurate estimate by noting the reading at rest and then when on plane. Since the hull will have a steeper angle on plane, the gas gauge will read a higher level than the actual level.

 

[Hookup1]

Hookup1 do you know what is left in the tank in gallons or litres when the Yamaha gauge starts flashing?

The bottom bar is sold when the sending unit is at 1/8 of a tank and starts flashing below that. Just remember that when you are at the point of the gauge flashing and you are on plane you are in the danger zone. When you come off plane you may (I have) stalled the engine out.

It's possible you have a bad or incorrectly sized sending unit. You should plan to pull your sending unit and use a wooden yard stick, wood ruler or paint stirrer to check the tank depth and compare to your sending unit. If it's not the correct length that could explain what you saw. It's also possible you have a bad sending unit. My gauges do not have any switch settings and only reports what it reads.

Specs say 150 and 156 gallon fuel tanks. When you pop the pie plate cover over the sending unit there should be a certification sticker there from the tank manufacturer to give you gallons.

 

[Sardinia306Canyon]

On my BW 23 Outrage i could estimate remaining fuel rather correct if i went alone aboard, sat on the leaning post and checked then. Always alone and resting!

If your engines and electronics allow that, use "Remaining Fuel" and not the fuel senders in the tank.
On all the boats i had that remaining fuel was correct with a difference of 1-2 Gallons of up to 300 gallons.
Just get used after refueling to at the amount of gasoline you filled and/or fill to full and set tanks to full.
I can do that either on my CL+ gauge or on my Garmin MFD's
Chris

 

[tech_dog]

You probably have a bad sender, or maybe the wrong sender for the tank. I had inconsistent readings for a long time, and finally replaced my sender. Upon pulling it out I realized someone had replaced it with a unit 1" shorter than OEM.

Going back to the exact match OEM sender got me back to consistent tank readings that matched reality.

T.