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Mackie 12

Fuel Tank Volume?

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Mackie 12

This going to be long winded as that is the only way I can somewhat explain it,

Pulling the boat out of the water last fall and I ran out of gas while waiting for wife to back in trailer. Put 5 Liters in and got the boat out of the water. Prepping for this summer and have the interior removed and notice that fuel tank actually has just about half a tank in it? Fuel gauge says on "E" basically but physically has half a tank? What am I missing here?

When I originally bought the boat (Last year) I had done the math on how much the fuel tank will hold so I new what to budget for on any given weekend which is 144 Liters @ $1.10 = $158.00 per weekend. Now on my first fill I was able to get 70 +/- liters in and that is. So I guess this has been a problem since I bought the boat.

Anyone out there have any idea's on what is causing this and how to fix?

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Fman

Is your sending unit bad? Sounds like it's not working anymore.

My boat says empty at about 1/4 tank. I just use hours, it's more accurate. I burn on average 5 gph. I know I can run 6 hours on water and still have plenty to get back to the dock.

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Mackie 12

I was thinking about that but if the sender is not working it will just show an inaccurate reading on the gauge and not actually shutdown fuel to the motor will it not?

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Woodski

@Mackie12: A blocked vent valve located on top of the tank can cause the issue you are referring to (engine stopping w/ ample fuel in tank), and a bad fuel pump can also cause similar issues as the inlet pressure drops as the fuel volume gets lower.

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Mackie 12

Woodski,

I was also thinking that, essentially vapor lock would it not be? Do you know what Psi it should be at pre and post actual fuel pump? It is easy enough to put in two gauges to monitor pressure.

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JasonK

Apparently you didn't run out of gas when you thought you did.

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JasonK

Maybe your kill switch lanyard got pulled out and that made u think u were out of gas. After putting the 5 liters in did you adjust/press/reconnect/ mess with the lanyard?

I'm trying to understand why the boat died and would not start until you added 5 liters of gas to a half tank. Maybe theres a pick-up tube in your fuel tank that came off.

Anybody know if the sender has any correlation to the fuel pick-up? Could they be the same unit?

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Mackie 12

Jason,

thats wehat I cannot figure out. I wonder if the fuel gauge sending unit is tied to the fuel pump some how and was telling it not to pull fuel? That is the only thing I can think of. If the fuel tank is empty (or thinks it is empty) will the fuel pump still try to run?

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phataz5

on the sender there are two wires one black and one pink , the pink one is the sender wire and the black is the earth, take the pink off and hold it on the black one and see if the gauge moves up and to fill ,that way you can see if its the sender .

Edited by phataz5

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GreenMan

I am confident that the fuel gauge reading has no influence whatsoever on the engine running. i.e. it does not have the ability to shut down the engine at all, let alone just because it thinks fuel is low.

I like the lanyard theory, though. They are a known reliability issue. Typically, if the lanyard switch has opened, the engine stops and the gauges shut down. Most other electrical equipment continues to operate.

re the gauge, they have dreadful resolution and accuracy. One problem is that the tanks are so shallow and then they are in a boat that rocks side to side. The sender float only moves up and down a small amount for a given consumption of fuel.

Does yours register well less than full when you know the tank is actually full? If so, sounds like the float arm needs to be adjusted. The float arm would need to be adjusted (bend the arm) downward.

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RTS

Prepping for this summer and have the interior removed and notice that fuel tank actually has just about half a tank in it? Fuel gauge says on "E" basically but physically has half a tank? What am I missing here?

What year is your boat? My '02 Sunsetter, and if I am not mistaken all the boats of that era, were shipped with fuel sending units that were about 1/2 as long as they should have been. That's why you need over 1/2 tank to register anything on the guage.

My dealer filled my boat up when I bought it. A few hours on the lake, and my guage was reading empty. I was worried about what I had gotten myself into, knowing it had a 35 gallon tank. When I filled it back up, it only took about 15 gallons....there was still roughly 20 gallons in the tank.

The solution? I installed a universal sending unit from teleflex, and carefully followed the directions on how to cut and install it for my tank depth. Results were a fuel guage with near automobile accuracy for the rest of the time I owned the boat.

Edit: And I just saw your second post about the engine not running....sorry, I can't help you there.

Edited by RTS

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Fman

To reconfirm your issue, your fuel tank was at half tank but the engine would not run? You filled the tank up and it then it was fine and started? I misread your post, I was initially thinking your fuel tank reading was inaccurate, as others mentioned your fuel sending unit would have not affect if the engine would run or not, as long as there is fuel in the tank. I will just throw this out, possible vapor lock? Have you changed the fuel filter?

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bcf2003

I say blocked vent or bad fuel pump. From my understanding, boat died, you thought you ran out of gas, you then put 5 liters in it and it started back up. The whole time you still had 20+ in it. When you cracked the fuel fill cap to put gas in you allowed the air needed into the tank making fuel flow again. It then fired back up. Try pouring gas out of a gas can without a vent, same concept. If not that then I'd say fuel pump.

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Mackie 12

After I put in the additonal 5 liters it was a real pain to start as any Carb motor is i guess. iam going to try and confirm the float actual will go all the way doawn and back up again just to make sure it works. And yes after everyone's thoughts I believe it was a vapor lock that occured. Is there a way to test a fuel pump? Hook it up to 12V and see if it runs? can you run them dry for a few seconds?

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