Im currently making my 70's bass boat into more of a bass boat style, meaning putting a back deck on it with compartments to store things.

one problem im running into is how to safely make a compartment for my gas tank.

option 1 i will make a actual compartment built into the deck with a lid on it, to put my portable metal tanks in

option 2 i use a plastic "bolt in" type tank and put it under the whole back deck.

my boat is fiberglass, option 1 will be using metal tanks that come in and out, option two will be the built in plastic tank. how do i vent the fumes? is it needed to vent them? what about ground it?

I don't think gas tanks require grounding. If you install an external fuel gauge on the drivers console it will require a hot lead and a ground. But the tank itself is not grounded. Plastic will not conduct electricity.

Plastic tanks vent thru the fill cap recepticle which is mounted on the outside of the hull cap(you will have to drill holes for this). Two hoses run from it the the tank, a large one for gas and a small one for air. Both hoses connect to the recepticle.

Metal tanks in an enclosed compartment: On older boats they vented the compartment using chrome scoops. One facing forward, one facing the stern. Mounted on opposite sides of the boat. Boat movement forces air in on one side and pulls out air on the other. Some boat manufacturers faced both scoops to the stern. The first option sounds better to me for better air flow but may allow water in during heavy rain or very rough water.............Al

Some boat manufacturers faced both scoops to the stern. The first option sounds better to me for better air flow but may allow water in during heavy rain or very rough water.............Al

I'm no engineer but seems that would act similar to cowl induction on a muscle car. Multiple scoops in line with each other would cause a backpressure forcing air into the compartment. Same thing the windshield on the car does.

thanks for the replies, guess i will get two vents on the compartment. as i have decided to stick with the metal transportable tanks.

I'm not sure you need vents. The only vent I have in my bass boat is a vent to let air back into the tank as gas is drawn out by the engine's fuel pump. Maybe I'm mistaken, but I don't believe the rear compartment holding the mounted tank is vented, unless you count the opening for the cables and wiring. Inboards are vented. In fact the standard practice is to run a blower or open the engine hatches and bilge hatches for a few minutes before starting the engine. Sparks from any source on the engine can cause fuel vapors to go boom. Once it's running any fumes that might leak or get into the bilge are sucked into the engines intake before they can accumulate.

On my gas engine powered lobsterboat I had two vents from the bilge. They were four inch pvc pipe with an elbow at each top. One faced forward, the other aft. Any air movement into one was drawn out at the other. I still removed the engine box for a few minutes before starting just to be sure. Starting an outboard produces no sparks in the bilge. But, it's never a bad idea to open a hatch to the fuel tank area and take a sniff.

I don't think gas tanks require grounding. If you install an external fuel gauge on the drivers console it will require a hot lead and a ground. But the tank itself is not grounded. Plastic will not conduct electricity.

Plastic tanks vent thru the fill cap recepticle which is mounted on the outside of the hull cap(you will have to drill holes for this). Two hoses run from it the the tank, a large one for gas and a small one for air. Both hoses connect to the recepticle.

Metal tanks in an enclosed compartment: On older boats they vented the compartment using chrome scoops. One facing forward, one facing the stern. Mounted on opposite sides of the boat. Boat movement forces air in on one side and pulls out air on the other. Some boat manufacturers faced both scoops to the stern. The first option sounds better to me for better air flow but may allow water in during heavy rain or very rough water.............Al

a metal tank should be grounded. also, please don't ever run a hot lead to a fuel sender. one gallon of gas is equal to 16 sticks of dynamite when ignited and if you make the sender hot you will blow things up. the sender uses a "send" wire that transmits ohms to the guage which will have posts for 12v+, 12v- and "send"(usually marked with an s)

any tank that is permanently mounted need to be vented to ouside the hull somehow. you can buy fuel fills that also work as the vent via a seperate hose. this is needed so the tank can allow air in to replace the fuel being taken out as Fishing Rhino described. for portable tanks you cannont put them in a closed unvented compartment. they vent by themselves thus enhancing the chance of fuel vapors inside the compartment. fuel vapors are far more volatile than fuel itself and require much lower temps to ignite. venting the compartment will help but is not fool proof.

my reccomendation is to have a tank made that is the size you want/need and plumb it in permanently and correctly.

a metal tank should be grounded. also, please don't ever run a hot lead to a fuel sender. one gallon of gas is equal to 16 sticks of dynamite when ignited and if you make the sender hot you will blow things up. the sender uses a "send" wire that transmits ohms to the guage which will have posts for 12v+, 12v- and "send"(usually marked with an s)

any tank that is permanently mounted need to be vented to ouside the hull somehow. you can buy fuel fills that also work as the vent via a seperate hose. this is needed so the tank can allow air in to replace the fuel being taken out as Fishing Rhino described. for portable tanks you cannont put them in a closed unvented compartment. they vent by themselves thus enhancing the chance of fuel vapors inside the compartment. fuel vapors are far more volatile than fuel itself and require much lower temps to ignite. venting the compartment will help but is not fool proof.

my reccomendation is to have a tank made that is the size you want/need and plumb it in permanently and correctly.

a metal tank should be grounded. also, please don't ever run a hot lead to a fuel sender. one gallon of gas is equal to 16 sticks of dynamite when ignited and if you make the sender hot you will blow things up. the sender uses a "send" wire that transmits ohms to the guage which will have posts for 12v+, 12v- and "send"(usually marked with an s)

any tank that is permanently mounted need to be vented to ouside the hull somehow. you can buy fuel fills that also work as the vent via a seperate hose. this is needed so the tank can allow air in to replace the fuel being taken out as Fishing Rhino described. for portable tanks you cannont put them in a closed unvented compartment. they vent by themselves thus enhancing the chance of fuel vapors inside the compartment. fuel vapors are far more volatile than fuel itself and require much lower temps to ignite. venting the compartment will help but is not fool proof.

my reccomendation is to have a tank made that is the size you want/need and plumb it in permanently and correctly.

Freebie------Ohms is a measure of resistance obtained by measuring the voltage drop in a circuit. In this case the sending unit is the circuit. To obtain an accurate resistance reading(ohms) the gauge must transmit a known voltage. Since the battery/charging system voltage can vary greatly the gauge uses the voltage from the battery/charging system and stabilizes it to supply a known voltage(lead marked with an S) to the sending unit and measures the voltage drop through the sending unit to determine the amount of gas remaining. I have never measured the voltage or current on a fuel sending unit but I would assume it is low however it is a hot(voltage present) lead. You can not have a resistance reading in a circuit(ohms) without voltage. Sounds a little scary I agree but that is how it works......................Al

The law usually requires that if you put a portable tank into a compartment it NEEDS to be vented. As is posted above usually 2 vents one facing forward one rearward. Grounding a fuel system is never a bad idea.

My boat has an air scoop pointed forward on one side and one pointed aft on the other.