Repairing leaking vent hose fitting at the fuel tank

[LakeTravisAlpha1]

My 1995 Wellcraft Excel 19 SX w/ 3.0 Mercruiser Alpha One LX has at least one leak where the 3/8" vent hose goes into the plastic fuel tank. I'd pull the tank and replace it, however this boat has been discontinued and the belly tank that lays under the floor has so far been impossible to find online. A new tank would have to be specific to my boat and be an exact replacement of whats there as there is zero space between the stringers and it has a V bottom that lays in the hull. So my only alternative is to fix what I have.

The boat has always been 'gassy' and I strongly suspected a leak somewhere. When I topped the tank off with fuel I noticed a wet circle around the vent hose fitting slowly growing larger. The vent hose has a silver metal cube or square fitting on the end that apparently attaches to a thin, silver, hex shaped collar on the tank. Below that collar comes the seepage.

Do I detach the hose from the box end and :
a. Unscrew that box shape fitting from the collar, then unscrew the collar from the tank?
b. Leave the box end attached and try and get an adjustable crescent wrench on the thin collar?
c. Does the thin silver collar on the tank screw into a plate in the tank or thread into the plastic tank itself?

I was hoping to unscrew the silver collar from whatever it's threaded to and applying a gas retardant sealant like Permatex under it.

Is this possible?

 

[LakeTravisAlpha1]

3.0 Fuel tank leaks at the vent hose

My '95 Mercruiser 3.0 Alpha One has a slight leak where the vent hose connects to the fuel tank. Gas creeps out between the bulk head fitting that attaches the 3/8" vent hose and the plastic tank. The boat is a discontinued Wellcraft Excel 19 SX and I've had zero luck finding a replacement tank to replace the belly tank so I have to fix the one thats in there.

I was hoping to get Permatex Gasket Maker under the bulkhead fitting, between the fitting and the plastic tank, but am not sure how to go about this. I have a tendency to make matters worse when it comes to mechanical repairs so I don't want to ruing this discontinued tank. Do I loosen the fitting enough with channel lock pliers to squirt Permatex under the fitting and screw it back down and if so how do I keep the inside fitting from just turning as there is no way to get in the closed tank and hold the inside fitting?

Hopefully there is a procedure as surely I'm not the first person whos ever faced this challenge.

TIA

 

[fishrdan]

Pictures of fitting on tank?...... From your description is sounds like a removable fitting, and should have a gasket to seal it. I wouldn't use any type of sealant on a plastic tank, gasket only.

If you're looking an odd tank size, check this place.

 

[Bondo]

Ayuh,...... One thread per problem, posted in One forum,... Not several in a few forums,....

Thank you,....

 

[LakeTravisAlpha1]

Pictures of fitting on tank?...... From your description is sounds like a removable fitting, and should have a gasket to seal it. I wouldn't use any type of sealant on a plastic tank, gasket only.

If you're looking an odd tank size, check this place.

I'm sure it has or had a gasket at one time, but my dilemma is getting a new one between the fitting and tank. If I am able to unscrew the 90 degree hose attachment from the outside ring, unless that ring has a mating ring thats permanently attached on the inside of the hole or the outside flange just screws directly into the tank, I'm screwed.

IOW, if I unscrew the 90 degree fitting thats clamped to the hose from the flat plate on the tank and a matching plate on the inside used to sandwich the plastic tank in between falls free inside the tank, there is no way to get it back in place on the inside ceiling of the tank. Therefore, I was thinking if I can unscrew the top flange or plate enough with channel locks without removing it completely from whatever it's attached to on the inside of the tank, I could squirt some gas resistant sealant like Permatex to form a new gasket. Then again, there may nothing on the inside of the tank, the flat flange may just thread into the thin plastic wall of the tank, but I doubt it.

Every side view drawing of a bulkhead fitting I've seen has a matching flange on the inside of the tank with the tank wall in between. And if there is a ring on the inside, unless it is somehow permanently affixed to the inside of the tank, it's going to turn when I try and loosen and re tighten the outside flat hexagon shape ring.

I can take a pic and learn how to attach it but you'll see its just a common vent hose fitting next to the same type 3/8" line fitting that goes to the fuel pump and the flat round fuel sender plate.

 

[harleyman1975]

Well keeping it from falling in is pretty simple you take the 90 degree fitting off and thread in a T shaped wire to help you hold it so it doesn't fall out of the hole. As to a seal or gasket silicone will eventually fail. whatever you use MUST be fuel proof not just fuel resistant. They make o rings that are for use around gasoline. This would be my plan.

 

[LakeTravisAlpha1]

Pictures of fitting on tank?...... From your description is sounds like a removable fitting, and should have a gasket to seal it. I wouldn't use any type of sealant on a plastic tank, gasket only.

If you're looking an odd tank size, check this place.

Thanks for the advise. I'm going to make one concerted effort to unscrew the fitting from the tank and if I don't run into a bunch of nonsense I'll gladly stick a rubber gasket in and hopefully put it back together. If not, I'm going to look seriously at the link you supplied for a new belly tank with new fittings and sending unit. Being on a fumey, floating bomb in the middle of the lake with people I care for is not a relaxing way to spend a day.

 

[Scott Danforth]

if the fittings threaded insert is molded into the tank, your going to need a new tank.

I would pull the tank out, take pictures of what you have. if it can be repaired, we will help. if it has to be replaced, we can help with that as well. if it has to be replaced, the manufacturer of the tank (and not the boat) will have a stamp on the tank. you could contact them for a replacment.

 

[Pocket Change]

I had a crack in the vent line fitting that connects the vent hose to the tank. It's welded to the tank. Used JB Weld to close up the crack. Hasn't leaked for 10 years. I think they make JB Weld for use on different materials. My tank is aluminum.