gas tank problems, water, vent

M

motorboater17

Recruit
Joined
Aug 14, 2012
Messages
5
I have a poly tank under the floor of a 17 ft Pro Sport CC. Had water in it, thought I got it out, tried a 6 gal old school tank, ran great. Put 30 gals. in it, drove to the beach, tank had sucked down and gas coming out, HELP
 
A

Another retired guy

Ensign
Joined
Jun 17, 2012
Messages
940
Re: gas tank problems, water, vent

What do you mean by "tank sucked down and gas coming out"? Has the tank imploded and gas has leaked into the bilge??
 
M

motorboater17

Recruit
Joined
Aug 14, 2012
Messages
5
Re: gas tank problems, water, vent

Another retired guy said:
What do you mean by "tank sucked down and gas coming out"? Has the tank imploded and gas has leaked into the bilge??
Click to expand...

the top side of the tank around the sending unit collapsed about 3 inches. Was pushing gas out thru the screw holes, I removed the unit, I could pull the top of the tank up, stopping the gas, let it go it went down and gas poured. Ran 5 gal out thru the bilge. Makes me think the vent is stopped up
 
M

motorboater17

Recruit
Joined
Aug 14, 2012
Messages
5
Re: gas tank problems, water, vent

motorboater17 said:
the top side of the tank around the sending unit collapsed about 3 inches. Was pushing gas out thru the screw holes, I removed the unit, I could pull the top of the tank up, stopping the gas, let it go it went down and gas poured. Ran 5 gal out thru the bilge. Makes me think the vent is stopped up
Click to expand...

it all started with water in the tank, pumped it out, changed filter, seperator, took a 6 gal tank to the lake and it ran fine, then I filled it up, this happened. Cant find a vent, unless the cap is the vent.
 
A

Another retired guy

Ensign
Joined
Jun 17, 2012
Messages
940
Re: gas tank problems, water, vent

For sure the vent is blocked. Must be there somewhere - is this the first time you've run this boat?
Maybe someone else on the forum is familiar with this boat?
 
M

motorboater17

Recruit
Joined
Aug 14, 2012
Messages
5
Re: gas tank problems, water, vent

Pro Sport 17 ft center console, 30 gal tank under the floor, been running it for 3 yrs
 
A

Another retired guy

Ensign
Joined
Jun 17, 2012
Messages
940
Re: gas tank problems, water, vent

So if it was working ok before draining the water from the tank, something must have been changed during that process. How did the water get in the tank? How did you drain it? When you hooked up the 6 gal tank you must have removed fuel hoses - have they been replaced correctly?
 
M

motorboater17

Recruit
Joined
Aug 14, 2012
Messages
5
Re: gas tank problems, water, vent

its all hooked up right, i took it loose from the in line filter, hooked that to the 6 gal tank. I think the sending unit wasnt tight, thats how the water got in, that and ethanol. I think now it has water in the carbs and I really wonder about the vent, what research i have done says it will run but not take gas if it is clogged. Also why did the tank sink when full, it should have vented out. Headed back down today and try to figure it out
 
U

UncleWillie

Captain
Joined
Oct 18, 2011
Messages
3,995
Re: gas tank problems, water, vent

motorboater17 said:
Pro Sport 17 ft center console, 30 gal tank under the floor, been running it for 3 yrs
Click to expand...

Your vent is plugged. It makes a favorite mud wasp home! :(

A 30 gallon, under floor tank will NOT be vented through the cap.
That would form a 30 gallon Molotov Cocktail.
The Vent fumes would settle in the bilge! :eek:

Find the Vent line, it goes through the hull, and clear it out. :D

Removing 1 gallon of fuel from a 30 gallon tank that has 6 gallons in it makes the air expand by <5% (0.5 psi)
Removing 1 gallon of fuel from a 30 gallon tank that has 29 gallons in it, makes the air expand by 100%. (7 psi)
The full tank will crush. the 20% tank will take it! :cool:
 
PWH1

PWH1

Petty Officer 3rd Class
Joined
Jan 11, 2010
Messages
78
Re: gas tank problems, water, vent

UncleWillie said:
I believe that is a "Deck Fuel Fill with Vent " fitting and not a tank gas cap.

An under floor tank will NOT be vented through the cap.
Click to expand...

Hmmmm.... I have a 18 gallon under deck tank that is vented exactly in that manner - combination gas fill/vent.

OP - start at the tank and trace the vent line... You should be able to quickly discern whether or not its venting to the fill cap or through a hull vent.
 
J

joewithaboat

Lieutenant Junior Grade
Joined
Jul 3, 2011
Messages
1,172
Re: gas tank problems, water, vent

My 30 gallon tank is under the floor and vented with a cap exactly like the one pictured above. Vent line attached just above fill hose.
Combo cap/vent.

I agree that the vent is plugged!
 
A

Another retired guy

Ensign
Joined
Jun 17, 2012
Messages
940
Re: gas tank problems, water, vent

It appears to me that there is some confusion in the replies as to whether it is actually venting under the deck, or not. It doesn't matter if there is a separate vent line from the tank, or from the vent cap pictured above, there HAS to be a line that goes to a thru- hull fitting. It can't just vent into the bilge!
 
bruceb58

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,478
Re: gas tank problems, water, vent

UncleWillie said:
I believe that is a "Deck Fuel Fill with Vent " fitting and not a tank gas cap.

An under floor tank will NOT be vented through the cap.
Click to expand...
They have the exact same thing that is a cap.
 
J

joewithaboat

Lieutenant Junior Grade
Joined
Jul 3, 2011
Messages
1,172
Re: gas tank problems, water, vent

Another retired guy said:
It appears to me that there is some confusion in the replies as to whether it is actually venting under the deck, or not. It doesn't matter if there is a separate vent line from the tank, or from the vent cap pictured above, there HAS to be a line that goes to a thru- hull fitting. It can't just vent into the bilge!
Click to expand...

No confusion here. My cap, like the one above, is mounted on the outside of the transom. "Thru Hull" has a fill tube and a separate vent tube both coming to the same fitting... vent/cap combo.
 
U

UncleWillie

Captain
Joined
Oct 18, 2011
Messages
3,995
Re: gas tank problems, water, vent

Maybe this is getting lost in the interpretation. (English is just so much fun!) :facepalm:

An under Deck Tank may be Vented Through the Tank Fitting.
But it should not be Vented AT the Tank Fitting.

The vent fumes should not be allowed to accumulate into a closed bilge.
The vent line from the Tank Fitting needs to go through the hull and overboard.

Certain OB boats with open slat flooring and an open bilge in the rear that have no enclosed areas are exempt.
A portable tank sitting on the floor that vents through the fuel tank cap directly to the air is acceptable in this case.
But this is NOT the case with the OP's boat.
It has a fully closed floor with storage below!

If you have a boat with an underfloor fuel tank that you fill at the floor fitting, and is vented at the floor fitting into the boat...
You should spell BOAT, B.O.M.B. :eek:
 
bruceb58

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,478
Re: gas tank problems, water, vent

UncleWillie said:
If you have a boat with an underfloor fuel tank that you fill at the floor fitting, and is vented at the floor fitting into the boat...
You should spell BOAT, B.O.M.B. :eek:
Click to expand...
Where do you possibly read that there is a fuel floor fitting here? Not even going to take into account that I have never seen a floor fitting in a gasoline powered boat.

So Willie, you didn't know that there is a combo/cap available. Why are you complicating matters here?
 
U

UncleWillie

Captain
Joined
Oct 18, 2011
Messages
3,995
Re: gas tank problems, water, vent

bruceb58 said:
Where do you possibly read that there is a fuel floor fitting here? Not even going to take into account that I have never seen a floor fitting in a gasoline powered boat.

So Willie, you didn't know that there is a combo/cap available. Why are you complicating matters here?
Click to expand...

I am well aware that both Fuel Tank Gas caps and Thru Hull Fuel Fittings are available with integral Vents. :)

If the tank is in the floor, and the tank is stated to have a "Combo Vent/Cap" and not a "Thru Hull/Deck Fuel Fitting," where would one assume the Vented Cap would be other than at the floor? :confused:

I suspect we are all actually in agreement and the problem is in the nomenclature. :D

When I hear the words "Fuel Tank Gas Cap" I envision a gas cap on the fuel tank.
I do not picture a "Gas Cap" on the side of the boat.

The "Combo Vent/Cap" is refered by the manufacturer as a "Deck Fuel Fill with Vent " and not a "Gas Cap."

(English is just so much fun!) :facepalm:

Fuel Fitting1.jpgFuel Fitting2.jpgFuel Fitting3.jpg
 
You must log in or register to reply here.
Top