I have been fitting a fuel tank into the bow of my Waverider Mustang and plan to fit a deck filler, however I am having trouble deciding where to site the vent to keep it out of the way of flying water. The vent I have is shielded with a little mesh screen but I still want to avoid wash etc getting in.

So my question really is to all of you that have inboard tanks, where is your vent?

Mine is piped to the engine well, high up on the side. It's a long run from the bow (although mine is a belly tank) but I thought it the safest place. You often see them on either the side of the boat or on the side deck but that seems risky to me on a boat that may get used in bumpy water.

Mines midships high under the side deck, looking to move it right aft to vent high up into the outboard well where the steering cable comes thro

As both you and Alacrity suggest the splashwell is a good location but its miles from my tank (well 5 metres of pipe anyhow). I imagine it is best to vent outside the boat due to vapour being heavier than air and the risk of filling the bilge with explosive fumes although I have been carrying two 30 litre portable tanks with venting caps without worrying about it.

The difference is - or at least as I see it - with portable tanks they are filled outside the boat. Fixed tanks are filled in the boat so if you overfill (not difficult to do) it is likely to come out of the vent pipe (as mine did in Ireland) as it is often a little lower than the filler & you don't want fuel mix sloshing around in the bilges. My vent pipe runs from the higher front of the tank in front of the front seat back to the splash well so that's a fair way.

NB my code of practice for construction of small craft states "ventilation pipes should be a minimum of 7/16" bore but in no case less than double the internal diameter of the fuel feed to the engine" also "the pipe must be extended to atmosphere outside of the hull and terminate in a suitable flame arrestor" and "the open area of the arrestor screen should not be less than the area of the vent line"

trust this helps!

Thanks for the replies. The vent I have does have a mesh screen which I imagine is the flame arrestor, and I guess it doesn't matter how long the vent pipe is so long as the tank can breathe.

Edit
Just bought six metres of tube to run back to the splashwell should be able to run it up inside the cockpit coaming out of the way.

might be 'stating the bleedin' obvious' but do ensure the pipe won't have opportunity to droop along its run, therefore creating an air lock if fuel gets in it!

Good point well made. I spent yesterday between showers contorting myself bonding attachments in place along the inside of the cockpit coaming I will install the pipe and check for droopage.

could always drop a Viagra tab into the fuel I suppose?