Running Out of Fuel - Half Full

[Verda13]

Good day all,
Ive been having an issue since buying my boat. I run out of fuel, but I can only pump 8 gallons into my 19 gallon tank.
I assumed that it was a busted fuel pickup tube, but I took it out this weekend and it seems fine (I replaced it anyway). Any suggestions as to what else it could be? Having 10 gallons of unusable gas is rather annoying.

Sea Ray 185 O/B
Mercury 125 2-stroke ELPTO

 

[Blorton]

Fuel pump good?

 

[alldodge]

My thought also, fuel pump getting weak or fuel line has a crack so your sucking some air

 

[ahicks]

Maybe a venting issue?

 

[mike_i]

I had the same issue with an old boat I had years ago. " I can only pump 8 gallons into my 19 gallon tank" this is your issue not pumping gas out. Fill the tank as much as you can at the gas station, your 8 gallons. Then fill a couple gas cans, go home. Detach the trailer from your tow vehicle. Lower the bow as low as you can then try to fill the tank and see if you can get more gas in the tank. Let us know what happens.

 

[Verda13]

Thanks for the replies!

Fuel pump good?

I wouldn't suspect other wise, I have not issues with fuel starvation for the first 8 gallons. But perhaps?

My thought also, fuel pump getting weak or fuel line has a crack so your sucking some air

Wouldn't that effect the power all the time?

Maybe a venting issue?

I'll check that out today, although I've never had an issue filling up.

I had the same issue with an old boat I had years ago. " I can only pump 8 gallons into my 19 gallon tank" this is your issue not pumping gas out. Fill the tank as much as you can at the gas station, your 8 gallons. Then fill a couple gas cans, go home. Detach the trailer from your tow vehicle. Lower the bow as low as you can then try to fill the tank and see if you can get more gas in the tank. Let us know what happens.

I can visually tell that it becomes totally full when fueling up. Here is a pic when I "run out"

 

[alldodge]

Wouldn't that effect the power all the time?

If pump has trouble drawing fuel up it gets to the point it can't do it anymore. Like a pump can only lift so high, a weak one may have the same in reverse

Another thought; being a 2 cycle, can you get it going again by squeezing the ball again? If not then its not the pump

Wonder if the tank was ever replaced with smaller one?

 

[Verda13]

If pump has trouble drawing fuel up it gets to the point it can't do it anymore. Like a pump can only lift so high, a weak one may have the same in reverse

Another thought; being a 2 cycle, can you get it going again by squeezing the ball again? If not then its not the pump

Wonder if the tank was ever replaced with smaller one?

Would it be so absolute? I can only use exactly 8 gallons. I cannot get the ball to stiffen up once I have "ran out" of fuel. The tank has never been replaced to the best of my knowledge. It would have to have been cut out

 

[alldodge]

Most would never notice if the tank was cut out and glassed back in

What is you pic showing?
Looks like about 10 inches to bottom of a insert tube

 

[Verda13]

Most would never notice if the tank was cut out and glassed back in

What is you pic showing?
Looks like about 10 inches to bottom of a insert tube

Is it showing my fuel tank. There is a hole by design (I'm not sure why) but as you can see it's 11" high and when it get down to 7" I "run out"

 

[alldodge]

The pic doesn't look like the drawing in latest post. My thought comes from the drawing I see a fill neck coming out of the tank, and the pic shows the neck going into the tank

That said, if (note the IF) were seeing gas through the neck and its "not" filling up the neck on the inside, that's not gas or something else is going on and is really weird.

Can the stuff on the bottom be scraped off?

Would that happen to be something like Por-15 maybe

 

[Verda13]

The pic doesn't look like the drawing in latest post. My thought comes from the drawing I see a fill neck coming out of the tank, and the pic shows the neck going into the tank

That said, if (note the IF) were seeing gas through the neck and its "not" filling up the neck on the inside, that's not gas or something else is going on and is really weird.

Can the stuff on the bottom be scraped off?

Would that happen to be something like Por-15 maybe

That pic is the of the "hole" in the tank, it is total enclosed, nothing was removed, it's just there and the grime is not "in" the tank. You can see it on the previous pic beside the sending unit. Here is another few pictures.

 

[Scott Danforth]

Is it showing my fuel tank. There is a hole by design (I'm not sure why) but as you can see it's 11" high and when it get down to 7" I "run out"

the hole in the middle is to mold in a support that keeps the top and bottom from flexing alot.

 

[alldodge]

ok got it, thanks
Then if the tank is 19 gallons then the pickup tube (old and new one which you replaced) is being bent so it does not reach close to the bottom. Or its not long enough

 

[Verda13]

ok got it, thanks
Then if the tank is 19 gallons then the pickup tube (old and new one which you replaced) is being bent so it does not reach close to the bottom. Or its not long enough

It is long enough and the old one didn't have any air escaping (based on me plugging one end and blowing into it). It is quite rigid, I can't see it bending.

 

[Blorton]

With the boat on the "new" empty, can you hook something else up to the pickup tube and see if you can pump any fuel out with something different?

 

[alldodge]

Only possibility I have left is wonder if the pickup tube goes into another tube in the tank. If it has something like this, maybe like putting the end of the tube in a Glass. The tube should have a hole near the bottom, but if its clogged up then it only gets fuel when its able to pour over the edge

No clue, just spit balling

 

[alldodge]

Get it where you run out and disconnect fuel line from tank and fuel cap.
Use a compressor and blow low pressure air back thru the fuel line into the tank. Do that and few times.

Reconnect fuel line and see if you can pump gas using the ball

 

[dingbat]

I've had something similar thing happen with my forward reserve tank.
54 gallon tank....would start acting up when things got rough. Would leave a 1/4 tank of fuel when it ran out

Never got completely to the bottom of it but resolved the issue by removing the anti-siphon valve, replaced a suspect tank select valve and ran new fuel lines from tanks to fuel pump.

I surmise the combination of a "flaky" anti-siphon value combined with leaks at the various hose fittings (fuel line was old and hard) was just enough to reduce the fuel pump vacuum of over the length of the system. The fuel pump had no problem drawing from the main tank setting at the same elevation. The only difference was 12' of additional fuel line

Try removing the fuel line from motor side of primer bulb to remove any residual back pressure and trying pumping when your tank is "empty".

If this doesn't work, remove fuel line from pickup tube. Connect a short piece of hose and primer bulb directly to the pickup tube and pump.

If that doesn't work you have a problem with either the primer bulb or an issue inside the tank.

 

[alldodge]

I've had something similar thing happen with my forward reserve tank.
54 gallon tank....would start acting up when things got rough. Would leave a 1/4 tank of fuel when it ran out

Never got completely to the bottom of it but resolved the issue by removing the anti-siphon valve, replaced a suspect tank select valve and ran new fuel lines from tanks to fuel pump.

I surmise the combination of a "flaky" anti-siphon value combined with leaks at the various hose fittings (fuel line was old and hard) was just enough to reduce the fuel pump vacuum of over the length of the system. The fuel pump had no problem drawing from the main tank setting at the same elevation. The only difference was 12' of additional fuel line

Try removing the fuel line from motor side of primer bulb to remove any residual back pressure and trying pumping when your tank is "empty".

If this doesn't work, remove fuel line from pickup tube. Connect a short piece of hose and primer bulb directly to the pickup tube and pump.

If that doesn't work you have a problem with either the primer bulb or an issue inside the tank.

Good point Ding
Baffle in the tank with a small hole at the bottom

Buddy bought a new holding tank and told the manufacture he wanted at least 2 inch holes need the bottom in the baffles. He gets the tank and only holes in the baffel is one large hole in the middle, 4 inches above the bottom, and one 1/2 place in the corners. Its a holding tank, how is crap going to make it past a 1/2 hole