Fuel tank screw hole repair

[McGillicuddy]

Kind of a silly question here but, it appears one of the sending unit holes on my fuel tank is enlarged and tapped for fine thread machine screw (maybe size 12) while the rest accept size 10 metal screws.

Can I reduce the size of the hole with some JB Weld or something or is there a better way. I really don't want to over drill a hole on the sending unit itself. Any thoughts? Thanks.

[pelican]

Originally Posted by McGillicuddy

Kind of a silly question here but, it appears one of the sending unit holes on my fuel tank is enlarged and tapped for fine thread machine screw (maybe size 12) while the rest accept size 10 metal screws.

Can I reduce the size of the hole with some JB Weld or something or is there a better way. I really don't want to over drill a hole on the sending unit itself. Any thoughts? Thanks.

screws should be 10-32 fine thread...maching screws - not self tapping !

jb weld,or anything else will prove to be a bad choice...

[Normagain]

For what it's worth, I have a friend that patched a hole in his small outboard water jacket with PC7 Epoxy and it is holding after several years much to my surprise. There is a PC11 that is supposed to be better for aluminum. Much better than JB Weld for this sort of thing but if over drilling the sender is possible, I'd definitely do that.

[McGillicuddy]

Originally Posted by pelican

screws should be 10-32 fine thread...maching screws - not self tapping !

jb weld,or anything else will prove to be a bad choice...

Thanks for the feedback guys.

Pelican,

I have used "water weld" to effectively seal an aluminum oil pan hole and it has held 5 years or more but that is different. Obviously I'm a little leery that an epoxy would hold up in such a minimal surface area application.

I see your point and concur that threaded 10-32 screws would offer better holding power and be less subject to stripping the holes (which probably happens due to over-tightening). I can still do that on 4 out of 5 holes. But I ask why tanks rarely come threaded, and why virtually all sending units are shipped with stainless deep thread sheet metal screws (sharp but not self-tapping).

The over-size hole is my immediate concern. Repair or adapt are my only options. What's the better way to resolve this? Over-drill the sender or some form of patch?

Leaning toward over-drilling the sender as Normagain opined.

Thanks.

[bilgerat]

Helicoil, if they make one that small

[pelican]

Originally Posted by McGillicuddy

Thanks for the feedback guys.

Pelican,

I have used "water weld" to effectively seal an aluminum oil pan hole and it has held 5 years or more but that is different. Obviously I'm a little leery that an epoxy would hold up in such a minimal surface area application.

I see your point and concur that threaded 10-32 screws would offer better holding power and be less subject to stripping the holes (which probably happens due to over-tightening). I can still do that on 4 out of 5 holes. But I ask why tanks rarely come threaded, and why virtually all sending units are shipped with stainless deep thread sheet metal screws (sharp but not self-tapping).

The over-size hole is my immediate concern. Repair or adapt are my only options. What's the better way to resolve this? Over-drill the sender or some form of patch?

Leaning toward over-drilling the sender as Normagain opined.

Thanks.

after 20yrs in the marine biz - i've yet to see a fuel tank,the area for the sender,the holes,not to be tapped,10-32,the area is usually double thickness for the tank...

"self tapping" screws will not seal...the cheap fuel sending units-these usually come with 10-32 screws,with a sealer that squeezes out,when the screw is fully tightened...

me,personally,i wouldn't use any kind of sealing product on a fuel tank - ever !

[pelican]

take a look at this picture,zoom in on the sender - pay attention to the screws - they're not the same all the way around - you should notice that...the owner of this boat,he did a similar thing as you're going to attempt.stripped threads,used a big self tapping screw-end result - take a look at the top of the tank,clearly it's "stained" around the sender - clearly leaking...


there's another way,to attempt repair - provided the tank's in good condition - if the threads pulled,odds are the tank's pretty old ...it appears you've had some problems with your fuel system...

[Normagain]

I'm not seeing where he said he was going to use self tapping. He said it was tapped to size 12 with machine screws. If the sender has a rubber gasket (I'm not sure how they are set up but I think so) a larger sized proper screw should be fine. If not, and it uses gas proof sealant like Permatex whatever, again, should be no problem.

[McGillicuddy]

Originally Posted by pelican

there's another way,to attempt repair - provided the tank's in good condition - if the threads pulled,odds are the tank's pretty old ...it appears you've had some problems with your fuel system...

Only problem I've had with my fuel system was a chunk of what looked like silicone in my supply elbow. I presume that was from the previous owners attempt at sealing the sending unit.

Other than these over-sized holes my tank is in good condition.

I tried to re-tap them at 10-32 but they are simply too big. 12-24 will require me to re-drill the flange on the new sender. Don't know if a M5 size will work or not.

I was hoping to generate ideas but you kind of left me hangin' for your "repair" suggestion. Did you have an repair idea?

Bilgerat's helicoil idea is cool but it'll run me $40 for a kit and I'll be waiting 2 weeks to get it off some backorder.

I also thought about epoxying some pan-head screws to the inside of the tank but the thought of snapping the bond should I need to get in there again is another potential miss.

Any repair thoughts? I'm all ears...

[gofastsandman]

Why maybe. Why maybe. Let me climb out of my box.

Why not clock the top collar and drill and tap all new threads. Split the dif. on the span.

Make a cone of something to catch the shavings. Spin the cone tight to insert. Open up the chute. Catch and remove.

Stiff wire on the outside of the cone may allow enough of a bend in it to provide happpinesss.

Cheers,
GFS