Petrol storage on deck - close tote tank vent / valve or not?

[Zozza 293]

My yacht is powered by a 6hp outboard.

 

I have an old anchor locker on up on the bow of the deck of my little yacht, which I had converted to petrol storage.  It vents overboard through the hull using the existing anchor locker through-hull already there.  The hatch lid for this converted locker is not water-tight, which is the way I wanted it.  That means any fumes have two avenues for escape.

 

However, sometimes I just leave the petrol container secured aft on the deck ready for the next time I use it ( I do disengage the fuel line), and I have been advised if I do this to leave the tote tank's fuel line valve unscrewed -- just like you do when you are actually using the outboard motor.

 

Why would I have been advised to leave the valve open?  Won't the petrol in the tote tank evaporate quicker, plus also allow small amounts of rainwater to get in and spoil the fuel?  Is it something to do with any pressure build up from the heat of the sun allowed to "escape" while the tote tank is on deck as he reason for leaving the fuel tank valve open?

 

When I store in the converted anchor locker on deck I do screw up that fuel line valve on the tote tank.

 

[grantmc 59]

Petrol does expand and contract with heat and cooling. So leaving vent open is good advice. It's in a locker so out of the weather.

 

From 15 to 25 degrees the volume of space it requires increases by about 1%.

The actual expansion coefficient of petrol is .00095 per kg per degree C. Diesel is .000824.

[Island Time 1,235]

But, it will evaporate more quickly if air is being introduced, expelled, and introduced again with warming/cooling cycles. The expelled vapor from petrol tanks I'd expect to be very flammable!  A plastic tote will also expand with the temp changes - more than the fuel will. You can keep them closed. In the tropics, our 20ltr jerry cans could hold 24 ltrs!

[Pumbaa 9]

My rule is vent open if connected to outboard closed if not. Fuel tanks can handle any pressure build up from the suns heat if it can't or if it leaks get a new one.

[Zozza 293]

Petrol does expand and contract with heat and cooling. So leaving vent open is good advice. It's in a locker so out of the weather.

 

From 15 to 25 degrees the volume of space it requires increases by about 1%.

The actual expansion coefficient of petrol is .00095 per kg per degree C. Diesel is .000824.

 

Hi Grant.

 

If I leave tote tank on deck I leave vent open.

But if I store it in the converted anchor locker on deck then I close the vent on tote tank.

[banaari 27]

Leave it closed if not in use, open with the outboard running, and try to keep the tank topped up as much as possible - the less air in there, the less water vapour to condense when the temperature drops.

[Zozza 293]

Leave it closed if not in use, open with the outboard running, and try to keep the tank topped up as much as possible - the less air in there, the less water vapour to condense when the temperature drops.

 

I.E vent always to be closed when not in use -- thats the way I am reading what you are saing, which is not what I am doing at the moment if I leave it on deck.

[Dambo 44]

My understanding is the fuel will also go off quicker if you leave it open.

[erice 732]

^

 

yup, my understanding too

 

modern petrol, esp. unleaded, is quite a cocktail

 

and the more volatile elements would be the first to leave the tank

 

eventually (years of venting) leaving something that smells like turps and fires about as well 

[Zozza 293]

Thanks fellas.

I think the best idea is the 'ole Occams Razor thing, i.e me to stop being a lazy basterd & after each use to close the vent and store the tote tank in the designated deck locker that drains overboard.