Just bought an old boat. the fuel tank is located in the bow behind the cockpit. Up high. I notice that the vent is just a tube three inches long sticking out of the back of the tank but not leading anywhere. It's just in the bow. I suspect when they filled the tank too high it leaked into the boat and down into the bilge and so they never filled it up too much.
I want to install a vent. Should the vent be placed in the deck (ie on the deck at the bow). Or should it go through the hull and be placed on the transom?

the vent is just a tube three inches long sticking out of the back of the tank but not leading anywhere.

If as you say the tank is up high and you can't run the vent any higher, a cheap and nasty quick fix would be to mount a 2 litre plastic dink bottle somewhere and run the vent to it, If you do overfill you would have a 1.5 litre leeway.
Not very elegant but would work.
How do you measure the amount of fuel in the tank?

gary

it's my understanding that the main purpose of the vent is to allow equalisation of pressure in the tank, is that correct?

lydia said..
Lead it inside but to a point higher than the filler
also make it very small diameter just a few millimeters

Bigger tanks you have to lead outside though as Cisco says but can get away with little ones if the area is vented

My tank is under the cockpit and the vent connects to the bilge pump outlet into the back of the cockpit. Not sure if it would work with your set up but useful alternative to another hole somewhere if set up properly.

as mentioned above, the main reason for having a vent on a small tank is for equalisation of pressure in the tank, and these thus use small diameter hoses.

you do need to be a bit careful to not overfill of course.

a vent exiting to the outside that is beefy enough to also serve as an effective overflow is probably going to cause you more problems than it solves.

Donk107 said..

Futurecruiser said..
My tank is under the cockpit and the vent connects to the bilge pump outlet into the back of the cockpit. Not sure if it would work with your set up but useful alternative to another hole somewhere if set up properly.

Hi Futurecruiser

My tank breather is also a dedicated fitting the back vertical face of the cockpit

The only issue I can see with having a bulge pump outlet into the back of the cockpit would be if the bilge had oil or diesel in it you would end up with a mess in your cockpit if you pumped the bilge out

Regards Don

Hi Don,

it drains into a covered area right at the rear of the cockpit near the drains and behind the steering position so even when pumping out it doesn't end up anywhere you can step in it. I actually like having it there as I always know straight away if the automatic pump kicks in for any reason. Always an unpleasant surprise!
Last time it happened I was in some heavy weather in Bass Strait and was panicking about which seacock might have given way only to find something had dislodged, fallen onto and burst a big cask of fresh drinking water, so in spite of some nervous moments thankfully the only outcome was an even cleaner than usual bilge!