Glen-L.com

The vent also needs to allow air into the tank as the fuel is burned.....try to run and outboard with the vent closed on a portable tank.....when the vacuum gets high enough,the fuel pump can no longer draw fuel and the engine quits

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Boat building can best be defined as an endless series of
tragedies obscured by the occasional miracle, followed by a good bottle of beer.

Don't Dream Your Life, Live Your Dream

OK, let me see if I got this correct.
Use a check valve in the vent line to allow air & water in, stop fuel going out.
Use high loop in vent line to stop water going in.
Filling vent is the filler neck since the lid is already off.

Is there any other way?

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God Bless our Troops; especially our Snipers

If installation space is at a premium, look for an integrated Deck Fill and Vent. The vent has a built-in flame arrestor.

Vented Plastic Deck Fills

Here's a photo of our fuel tank installation. A 5/8" fuel vent hose with a high coiled loop is routed to a stainless steel fuel vent fitting installed on the sheer.
The coiled loop should be mounted as high as possible and the hose should be run 'downhill' to the sheer so that water can't find its way back into the tank.
We've installed a fuel vent whistle in the vent line to indicate when the tank is topped up.

Click here for more photos.

If you don't have the space to install the high coiled loop, install a P-trap fuel vent or a P-trap with fuel surge protection.
Both designs provide fuel tank venting and resist water intrusion into the fuel system.

90° P-Trap Vent


90° P-Trap Fuel Surge Protector

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Paul Kane Chelsea, PQ

Building the Glen-L Hot Rod : http://www.boats.chelseacoachworks.com

The two key issues is to make sure that your fill and vent line has some distance between the fill and the tank, which allows for expansion of even a filled tank, not withstanding when you are filling a built in tank from a fuel pumping mechanism. At the minimum the vent line needs to be about four times the distance than a close quarter fill hose.
This is where the loops come into place. But also keep in mind that horizontal loops are used in smaller and less freeboard boats and need to run foward in most all cases so that when the tanks are full and your boat is on plane the vent lines does not fill and create a potential natual siphon too when a tank is topped completely off.

If you are not mindfull of the actual distance, you will probably have issues of spillage when the tank is full or when the boat is even sitting in a warm garage dormant or under a cover. If you are running a two stroke engine where your oil is mixed in the gas, when it self vents on expansion, you have a mess too in its surrounding areas.

Great info!! I'm getting ready to do this so this is very helpful.

Roberta

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Roberta
Built Zip "Oliver IV" and Super Spartan "Jimmy 70"