Always Vent an internal fuel cell?

[jiminmontana]

My 35 gallon fuel cell is on the way.
http://www.moellermarine.com/aftermarket/fuel_storage_tanks/permanent_tanks/ Product # 032535 Product Dimension: 69.50L x 16.00W x 8.00H

Do ALL internal/below-deck fuel cells need to be ventilated with an outboard motor? This one will go between the stringers in an isolated compartment with a sealed access panel in the deck for maintainance. These tanks need room to expand as they absorb some of the fuel. The rest of the under sole will likely be filled with expanding, pourable foam. If so, do I plumb an air passage from one of the gunwales, opening to the fore part of the fuel area, then exiting out the aft with another piece of plastic tubing? What diameter tubing?​

 

[fishrdan]

Re: Always Vent an internal fuel cell?

Yes, your fuel tank needs to be vented. It depends on where the vent connection is on the tank as to where it will vent, fore-aft. I believe the vent hose is 5/8".

Moeller has a fuel tank installation guide on their website that will probably answer most of your questions.

 

[tashasdaddy]

Re: Always Vent an internal fuel cell?

fuel pumps cannot suck out of a vacuum. it would be very hard to fill a tank without a vent for air to escape.

 

[Bondo]

Re: Always Vent an internal fuel cell?

This one will go between the stringers in an isolated compartment with a sealed access panel in the deck for maintainance. These tanks need room to expand as they absorb some of the fuel. The rest of the under sole will likely be filled with expanding, pourable foam.

Ayuh,... Don't seal the bilge so well,...
Anywhere that there's the possibility of Gas, or a Gas Leak, Must be Vented....

 

[jiminmontana]

Re: Always Vent an internal fuel cell?

I'm sorry; why not seal the bilge too well? What does that mean?

 

[jonesg]

Re: Always Vent an internal fuel cell?

Don't make it airtight with foam, you'll be needing to install an air intake hose( not into the tank) to ventilate the tank compartment, also need an exhaust hose to the other side of the boat. They're usually 4 inch dia, mine look like dryer hoses ( laundry drier). I installed an inline fan in mine to push the air.
You don't need the fan with outboards but it doesn't hurt.
Do you have vents under the gunnels on your hull?
or is this the first time it has internal tanks?

 

[jiminmontana]

Re: Always Vent an internal fuel cell?

This old boat I am restoring has never had an internal fuel tank. I plan to vent the fuel area with air coming in from the port bow area and exit the starboard stern area. I can't see how the tank could pop, but I do see that it's a legal requirement -- no big deal. The attwood louvers look cool, but I need them to be flush -- the LoneStar Caribbean is designed for walking on top of the gunwales.

Should be easy to install the vent system since all the wood is being replaced.

Who makes a good in-line fan? Does it need to be pushing the air before reaching the fuel area? I'm wondering if it makes sense to have an electric motor running in the midst of gasoline vapors.

 

[jspano]

Re: Always Vent an internal fuel cell?

i had/have a bow mounted alum. tank. all tanks need vents or it would hard to fill and even worse to get gas to flow to the motor. the tank should come equiped for both. you need to be able to displace air and liquid. unvented tanks could collapse, think of trying to suck the water out of a 12 oz bottle without letting any air in

is this tank a hard one that keeps it's shape even when empty?

mine had a fill up front on the bow and a clear plastic looking one(you could put your finger in it,to get an idea on the size) and the po ran it all the way to the stern to vent, or you can mount a vent high on the outside. they make them just for that purpose.
if this is a real tight space, vent wise you might want to have some positive vent. there just in case some vapors get out

hope that helps

 

[jonesg]

Re: Always Vent an internal fuel cell?

This old boat I am restoring has never had an internal fuel tank. I plan to vent the fuel area with air coming in from the port bow area and exit the starboard stern area. I can't see how the tank could pop, but I do see that it's a legal requirement -- no big deal. The attwood louvers look cool, but I need them to be flush -- the LoneStar Caribbean is designed for walking on top of the gunwales.

Should be easy to install the vent system since all the wood is being replaced.

Who makes a good in-line fan? Does it need to be pushing the air before reaching the fuel area? I'm wondering if it makes sense to have an electric motor running in the midst of gasoline vapors.

The external vent louvre screws to an under gunnel manifold or collector box, the 4 inch air hose attaches to that with a ring clamp, the elec vent fans are spark protected, they cost around $25. The air hose just terminates in the tank compartment, thats where I installed my vent fan, just slip into the end of the hose and use the zip tie. Run it for a few seconds to see if you smell fuel.
You can source it all here on iBoats,
http://www.iboats.com/Shields-400-V...78892135--**********.817704553--view_id.22107

They sell the louvres and collector boxes here too.