Fuel evaporation

[Lukas]

Fuel Evaporation

I am looking for advice on the current fuel tanks I have.
On my Bass Challanger I have a plastic fuel tank like many of you do, on the cap you have a breather screw that you loosen when you take the boat to the water, ones the boat goes to storage you close the screw-valve and no fuel can evaporate.

With my new boat I have 2 build in fuel tanks with shiny chrome screw in caps with little breathing holes. Now when I get close to the boat in the garage I can smell fuel leaking but I found that it is the fumes from the caps obviously I am losing fuel due to evaporation. How do I seal these 1-2mm holes, currently I have stuck isolation tape over them just as a temporary solution? I need something more permanent to screw in and out as and when I use the boat.

Do one get caps with these relieve valves attached or do you get the small valves of the shelf and get them engineered into the chrome caps?

[andrer]

If I were you I would leave some room for evaporation.. On a hot day you might expand/damage your tanks due to pressure...!!!??

[Lukas]

Andrer, I did think of that but the boat is in the garage while the fuel is evaportaing. The problem is not when we on the dam or in the sun because then the breathing holes are opened for easy flowing for the motor. It is when it is in storage that I smell fuel fumes so for now I have stuck some tape over the holes but I need a more permanent vent screw solution.

[andrer]

buy some small none return valves or pressure relief valve or something so expanded air can escape but will keep it closed unter normal conditions

[bmas13]

Some of the fuel that you may be smelling is from fuel evaporating from the fuel line. Because the fuel sits in the lines (horizontally) it sometimes leeches out through the rubber hose, hence the vapors that you smell. I would also check and make sure that all of the hose clamps are tight (mainly from the inside of the fuel cap to the tank). You really don't want to plug those holes up.

[Lukas]

You really don't want to plug those holes up.

Thanks bmas13, I had to learn the hard way. They add alcohol to SA fuel, one of alcahol's biproducts is water, when you seal your tank make sure the tank is filled right up to the cap if not the water in the alcohol condensate and drips back into the fuel creating a real mess at the bottom. Obviously the motor sucks in the fuel from the bottom and your entire day and budget for the next ten trips are spend on flushing tanks, caburetors and fuel pipes. My boat is still in the shop due to this. Thanks for the advise. Best for me is to put just enough fuel for the day and leave my tanks breathing. Evaporating fuel is cheaper than the exercise i am going through at the moment.