Fuel Sender Mounting Trouble

[daniel123]

I am replacing a stock fuel sender on my Osprey's 45 gallon poly tank with a new WEMA model. After removing the rusted stock unit and mounting screws, I found that only three of the five threaded holes surrounding the access hole have viable threads left to accept the new mounting screws. One is stripped and at least one size larger in diameter and actually looks off-round; the other just appears to have damaged threads that don't allow the mounting screw to get started but otherwise may be ok.

The good news is that the three working mounting screw positions surround the plate, so there are three secure points of contact to compress the rubber gasket pretty evenly around the access hole. I have put the new unit in place and torqued down a bit on the working screws and they seem to hold it well and compress the gasket. I have not attached the wires, anticipating that I will want to do more to secure the mounting plate.

My question now is, what do I do next? Even if it appears that the three mounting screws are holding the sending unit plate securely in place, compressing the gasket to keep it air-(fuel-)tight, I assume I should do something to try to get it better secured. Should I get a threading/thread-cleaning tool and try to fix/clean the thread on the one (cross-threaded) hole? Should I fill the over-sized hole with Marine-Tex or JB Weld and insert a screw before it sets to get that section tight? Coat the plate with sealant?  

I welcome members' advice.

[fitz73222]

Why don't you use the next size up self tapping screws since the tank is plastic anyway. I realize that the other screws are machine screws but I don't see any issues. This is what I would do if faced with this situation.

[daniel123]

That's an idea, but are the threaded receiving holes actually in plastic? It feels like they are in metal, maybe a brass insert of some kind? I'd have to go to the boat, unwrap her and confirm, but at the moment Sandy is dumping 50 mph winds and the earliest snowfall in years here in OH-IO...

[flounderpounder225]

there is probably some type of nutsert in there, and probably fine thread machine screws? you could probably retap the existing holes going to same size but course (NC) thread.  OR... turn the entire sender a few degrees and re-drill all new holes and insert the rivnuts... here is an example...  http://www.amazon.com/Nutsert-Tool-Kit- ... B0040CZ608  I would go with the re-tap method first, then if it doesn't work go the other route..

[daniel123]

Marc,

That turning/redrilling idea's great! Let me hear some feedback on it from fellow members while I study that link...

Thanks!

Dan

[fitz73222]

Sounds like a good alternative as long as the tank is drained and fully evacuated of all fumes. Ever seen the brushes light up in a drill? Not a good idea over gasoline... But why not just re-drill the damaged holes to a larger size and re tap them and leave the sender in place?

[Whitewater]

I have to agree with Fitz drill and retap sounds like the right way to go but more importantly you are going to need to venturi and dead that tank unless you can get your hands on an air drill.

[TheKid]

Why don't you use the next size up self tapping screws since the tank is plastic anyway.

X2

[daniel123]

Sorry if I'm not up to code-speak, guys, but what does venturi and dead and X2 mean?

[gran398]

I think they mean you don't want to blow the thing up, times two.

I like the air drill idea. I don't have one, but my neighbor does.

[Whitewater]

Sorry if I'm not up to code-speak, guys, but what does venturi and dead and X2 mean?

Sorry I did not mean to be confusing.  I should have explained it more. In a prior life used to build and remodel Gas stations for Mobile and Sunoco so it is old hat to me. We used to remove the old steel tanks that had absorbed years of fuel into the pores of the metal so in order for us to haul it away we had to cut them up to scrap.  Obviously cant do this when there are fumes so these tanks had to be deaded with a venturi.

You would need to drain the tank of all fuel and then a Venturi is a cone shaped contraption that mounts ot the tank opening and hooks up to an air hose at the small end of the cone closest to the tank opening. You run the air through the cone and it drafts up using the tank vent as a draw to circulate and move the air out and up out of your breathing path.  Think of the movement of air like a smoker grill without the heat;  air is drawn in one side and then out the other but the circulation is the key to dead the tank (meaning that there are no longer any fumes left inside of it to spark and ignite)

You could always rough it by just shoving the end of the air hose off the compressor into the tank to circulate from the inside out but it takes longer and the key to this is not leaving any sort of metal end on the hose as under pressure it will flail and may contact and spark thus boom boom boom.  I saw a guy do this once and left a brass end with a steel hose clamp on it flopping around inside the steel tank like a bluefish on deck.  It sparked, ignited and sent a 10k gallon steel tank rolling and skidding 60 feet before it hit and totaled a parked car.  

This is why I would recomend just using an air drill if you can get it. Eventually all of our tools in that trade went to air.  To be honest you said this was brass set into the plastic?  Brass is soft, you could probably just turn a hand drill and you would tap by hand anyway I would assume.



Now I fear I may have explained too much  

[xo4001]

Can you use this?
http://www.wemausa.com/tank-sensors/det ... ensors.htm

[daniel123]

That ring might do the trick. I'd have to re-drill all five holes down all the way through the tank (the stock threaded female holes bottom-out now). Would that require an air-drill? What concerns are there with shavings that fall into the tank when you drill through? I'm not even sure if they are brass or stainless or plastic or what; I was hoping a member might know what material (plastic or metal nuts) was used to secure the fuel sending access in 1999-vintage stock tanks (Osprey 200).

Thanks for the help, Bahama!