Fuel evaporates and engine leaking fuel

[Marinescout]

Ok so we had a small snow storm so hadn't had a chance to work on boat because no heat in my shop yet. So I had a question when I went to pick my boat up I had to add fuel to it. I had about a 1/4 tank when I last left it but it's been awhile and I had zero in it when I got there the other day. I have a built in tank on the back side that is plastic with only a sun deck over the top nothing covering the sides. Could the heat of the sun be evaporating my fuel out? Also I had the motor tilted all the way up the other day and noticed gas had poured out the front of the engine but I do not know where it came from. Any help or suggestions would be great. Thanks suntracker 20 ft pontoon mercury 2 stroke 75. I also have this in mercury outboard help also if interested in reading and helping on that topic. Thanks

 

[MH Hawker]

sounds more like the heat is forcing fuel up to the motor to a leak

 

[RobertThoreson]

Hawker sounds right. The pressure build up in the tank is forcing the fuel to the motor and with the motor tilted all the way up, the float is not doing its job properly and along the fuel to run right out

 

[Scott Danforth]

couple the above with a day/night cycle that repeats and the tank is probably pumping itself dry.

guessing the vent isnt open. if it was, it would evaporate a bit, but not pump with the thermal cycles.

 

[ahicks]

Many installations have the tank located above the carbs (or possibly some of the carbs). If the needle and seat on one of those carbs is leaking a little, over a period of time it would be easy to see how 1/4 tank of gas could siphon into an engine. That would be my bet here.

The only evidence of that happening might be a fuel slick floating on the water around your engine if it's really calm out. Then again, you might not notice a thing....

 

[Marinescout]

I noticed the vent is broke on my gas cap so I will be replacing that. and I just had the carbs rebuilt so hopefully it will not leak anymore. Thanks for the help it has seemed to always loose gas out of the tank for the years I have owned it.

 

[MH Hawker]

try un hooking the fuel line at the end of the days use

 

[GA_Boater]

Deleted this same subject you added to your motor thread. One place is good enough.

How long is "it's been awhile"? And what do you mean the vent is broken? The vent is broken closed or open? Broken closed means the motor would starve for fuel in a short order because the closed vent will stop fuel flow. Broken open means the situation you describe wouldn't happen because the tank pressure is relieved through the vent.

Or you tank has a leak maybe? It happens. Also you said the carbs have been rebuilt. Is fuel still leaking from the carbs when tilted or could it be spilled fuel from the carb work?

 

[Marinescout]

I had the cards rebuilt since the fuel has been pouring out when motor was tilted up. Haven't tilted it up since to see if it still leaks. The vent is a small plastic screw on top of the larger plastic cap. The screw just freely spins and you can pull it up and down freely but not out. I'm not sure if it's blocked or not. I don't have any fuel smell around the tank like I would think in a leak situation. It sits sometimes for a few months between uses but normally only a few days when it's running good but that hasn't been to often in the past two years

 

[Marinescout]

Unhooking it is not an option as it's hard lined into the motor and tank.

 

[MH Hawker]

suntracker 20 ft pontoon mercury 2 stroke 75. I also have this in mercury outboard.....as you stated its a out board so it has a quick disconnect fitting and a rubber line at the motor even if its a hard line from the tank so its starting to sound like BS to me

 

[ahicks]

Not if somebody has by-passed that connector and has run the fuel line directly to the fuel pump. Not suggesting that's a wise move, only that it is possible. On a pontoon, as often as you actually need to disconnect that fuel line, I suppose you could make a legitimate argument on the necessity of that set of connections - given the potential for leaks and maintenance requirements there.

 

[Marinescout]

It is hardwired into the fuel pump on the motor side been that way since I bought. I thought it was suppose to be that way. What do you mean by bs? Are you talking about me or what? I come here for help not to be bashed and I hope that's not your intention on here

 

[Marinescout]

It has a permanent tank so I didn't think nothing of it having a permanent fuel line. There's a short piece of rubber coming from motor out of the hole in the front and the fuel line connects to that via a plastic hose fitting and clamps. The short piece goes to fuel pump. I will put a quick connect on it as soon as possible. Why don't you (Hawkins or hawker ) or whatever it is take a pic of your set up so I can duplicate it. It would be nice to see how it suppose to run from the tank to the separator then through the bulb and to the fitting and from fitting into engine to fuel pump. My separator is bypassed also so that would be nice to see how it suppose to be done and then I'll be able to actually get it fixed the non bs way

 

[GA_Boater]

Is your tank one of the Moeller red plastic ones? You can get a replacement vented cap here.

Typically a Mercury outboard will have some type of connector to disconnect the fuel line at the motor end. The tank may have a hard barbed connection or the same type as the removable motor end.

 

[ahicks]

You do realize none of this has anything to do with your fuel leak/disappearing act, right?

 

[MH Hawker]

+i would be happy to, in fact a few of your set up will help a lot

 

[Marinescout]

No sir it's a clear but now yellowish colored plastic tank with a black cap and a pickup tube with a metal fitting that the fuel line is clampd straight to the only thing else on the tank is a sending unit but my gas gauge does not work so.

 

[Marinescout]

I will take pics in the morning. Any help would be great. What does it have to do with?

 

[Marinescout]

What does it have to do with?