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Stripped and leaking fuel sending unit

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Stripped and leaking fuel sending unit

Old 01-25-2019, 07:24 PM
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Default Stripped and leaking fuel sending unit

So I replaced my broken sending unit. It was a pain to get to as the access hatch is 5” off. So you only can see the sending unit at a angle. 2 of the 5 bolts where stripped out and the hole of the tripped out bolts took a 5/16” tap. I was able to tighten the two stripped ones a little but I couldn’t crank down on them in fear of stripping it again. After taking the boat out a couple times I noticed I still have fuel seeping around the sender. So the question is is there any sealant I can use to install the sender unit? I was thinking of pulling sender and installing it wet sealant and installing the bolts wet with sealant on threads. Is there a sealant I can buy locally in south Florida? Or any other way of fixing the tank? I have only about 2” of space between the deck and the top of the tank.
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Old 01-25-2019, 08:03 PM
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5200
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Old 01-25-2019, 08:12 PM
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Permatex.
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Old 01-25-2019, 08:28 PM
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Originally Posted by Jonnyu View Post
So I replaced my broken sending unit. It was a pain to get to as the access hatch is 5” off. So you only can see the sending unit at a angle. 2 of the 5 bolts where stripped out and the hole of the tripped out bolts took a 5/16” tap. I was able to tighten the two stripped ones a little but I couldn’t crank down on them in fear of stripping it again. After taking the boat out a couple times I noticed I still have fuel seeping around the sender. So the question is is there any sealant I can use to install the sender unit? I was thinking of pulling sender and installing it wet sealant and installing the bolts wet with sealant on threads. Is there a sealant I can buy locally in south Florida? Or any other way of fixing the tank? I have only about 2” of space between the deck and the top of the tank.
Cut a larger access to repair properly. I'm sure you're mistaken about the 5/16 tap. The screw's are probably #8 or #10. Never use 5200 on a fuel tank, that is very bad advise. There is a product called gasoila that is used for gasoline but really you should never use sealer on a sender, the gasket is what seals it and should be installed dry.
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Old 01-25-2019, 08:45 PM
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Originally Posted by slickster View Post
5200
FYI from the 3M website
3MTM Marine Adhesive/Sealant 5200 is not recommended for use as a teak deck seam sealer. Extended exposure to chemicals (teak cleaners, oxalic acid, gasoline, strong solvents and other harsh chemicals) may cause permanent softening of the sealant.
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Old 01-25-2019, 08:52 PM
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If you can re-tap the stripped holes to the next size, fine. Just use Permatex to seal it, (#2, I believe). If you can't re-tap consider using a split ring insert. It goes inside the tank and sits up against the holes. A bit tricky to do, but it's sort of a last resort.
Blank Plates, Sender Plates, Split Rings & Gaskets
Click on additional info for dimensions
Bottom of page shows replacement screws and Permatex.
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Old 01-25-2019, 08:54 PM
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Originally Posted by sjef View Post
Cut a larger access to repair properly. I'm sure you're mistaken about the 5/16 tap. The screw's are probably #8 or #10. Never use 5200 on a fuel tank, that is very bad advise. There is a product called gasoila that is used for gasoline but really you should never use sealer on a sender, the gasket is what seals it and should be installed dry.
I wish I was confused about the 5/16. 1/4” tap falls right through. I was thinking about using life caulk. If not I would need to go to aviall prc 890. It’s was we use to seal fuel tanks in aircraft. I just want something I can buy at West Marine or similar
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Old 01-25-2019, 09:00 PM
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I wouldn't use Life Caulk or Life seal, Gasoline will loosen it. I've used Permatex on a lot of sending units, never had a problem.
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Old 01-25-2019, 09:14 PM
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you could possibly turn the sender a 1/16 of a turn and drill and tap (10-24) new holes. If you are not extremely careful you may risk a fire. but,,, if you blue tape over the hole and be very careful. it can be done.
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Old 01-25-2019, 10:47 PM
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Did you actually remove the sender and carefully inspect it for cracks and make sure the mating surface on the tank top and sending unit flange are smooth and not loosely corroded/ in need of cleaning up?
if the gasket looks the slightest but iffy , replace it. 5 Hole Gasket for Electric Sending Units (Includes Mounting Screws) |

If a 1/4"dia tap falls right through it sounds like others have previously stripped & enlarged those holes for greater dia. screws . Or corrosion is so bad nothing will hold for long.

I wouldn't use sealer there. Senders should be pretty easily removable. You will be kicking yourself if your sender fails and needs replacing. Besides the difficulty in separating parts with sealer then , some of the debris will end up in the tank headed for the pickup.

On at least of couple of my boats over the years including the present one, the 5 little sender screws have both tiny nitrile O-ings and plastic washers to effectively seal fastener holes, and after long intervals the gaskets get replaced to maintain the seal..

Rather than making the screw holes even larger and more prone to leakage, you might consider use of a tank sender hole repair "split ring" on the inside. It would use standard size sender screws.
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Old 01-26-2019, 04:47 AM
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Originally Posted by Jonnyu View Post

I wish I was confused about the 5/16. 1/4” tap falls right through. I was thinking about using life caulk. If not I would need to go to aviall prc 890. It’s was we use to seal fuel tanks in aircraft. I just want something I can buy at West Marine or similar
I don't know what's available at West Marine but the Gasoila that I mentioned is available from Amazon and is for use around gasoline. I'd stay away from Permatex, although it might be a temporary solution it does not hold up long under gas. The split ring would probably be a better solution.
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Old 01-26-2019, 05:07 AM
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You will need good clear access to sending unit for any effective repair. Cut bigger deck access hole or pull tank if it’s not too difficult. Aluminum and PE tank sender mounting plates are both soft compared to screws so OEMs recommend mounting screws should not be overtightened; you have to allow the gasket to seal the gap.
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Old 01-26-2019, 06:09 AM
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wait there's one more option,,,,,

Find an inept >but fully insured< mobile repairman with a blowtorch to repair the sender. After the fire dept leaves, you simply file a claim and wait for your new boat.
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Old 01-26-2019, 06:23 AM
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Originally Posted by LeakinLena View Post
You will need good clear access to sending unit for any effective repair. Cut bigger deck access hole or pull tank if it’s not too difficult.
There is a lot of truth here.

I would carefully drill out the holes and use 1/4-20 riv nuts.
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Old 01-26-2019, 10:22 AM
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Originally Posted by sjef View Post
I'd stay away from Permatex, although it might be a temporary solution it does not hold up long under gas.
Permatex PermaShield Fuel Resistant Gasket Dressing and Flange Sealant
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Old 01-26-2019, 10:24 AM
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Originally Posted by TTaxi View Post

Rather than making the screw holes even larger and more prone to leakage, you might consider use of a tank sender hole repair "split ring" on the inside. It would use standard size sender screws.
Blank Plates, Sender Plates, Split Rings & Gaskets
Read post #6.
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Old 01-26-2019, 10:34 AM
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Originally Posted by slickster View Post
5200
Have you actually used 5200 on a sending unit? Know someone who did? Please explain.
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Old 01-26-2019, 10:57 AM
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That's a far cry from the #2 that you suggested but would probably work. I like the Gasoila because it's made for use around gasoline and I know guys that service gas station pumps and hoses and that's what they use. I do believe any sealant should be a last resort though when dealing with a gas tank in the bilge.
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Old 01-26-2019, 11:04 AM
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Originally Posted by sjef View Post
That's a far cry from the #2 that you suggested but would probably work. I like the Gasoila because it's made for use around gasoline and I know guys that service gas station pumps and hoses and that's what they use. I do believe any sealant should be a last resort though when dealing with a gas tank in the bilge.
I agree about the sealant being a last resort. Should only have to use the rubber/neoprene washer and screws that have the seal built on to them, but with the over sized holes now, I think he's going to have to load up the screws and around the holes with sealant. I wasn't sure exactly what # Permatex I used, That's why I said, "I believe" in my original post.
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Old 01-26-2019, 11:12 AM
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This is a repair that needs to be done correctly. Any "resistant" sealant is bound to fail and then the sender will leak. Gas is nothing to play with! Measure up the area and purchase the smallest access hatch that will be large enough to expose the sender. You may be able to remove a larger section of the floor and uncover the entire tank. Use the thread repair devise of your choice helicoil, rev-nut, backing plate, etc. Install the sender correctly with all screws and a new gasket. Have peace of mind .
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