sending unit question

[slvrlng]

A few days ago I saw that the cold air was coming south. Since it had been raining a good bit and the boat is only on a slight incline in the driveway I knew there was some water up in the bilge in the bow. I decide to try to drain it out and pulled the boat forward up the rise in the driveway until it would  drain. I walked to the back of the boat and was checking out to see if it was draining and not clogged up with debris. When I got around the back I noticed a really strong gas smell. I had just filled up last week and it is stuffed to the rim. I quickly got a glass jar and caught the last of the fluid coming out of the garboard. Yep water on the bottom and really fresh gas on top. WTH! I let it drain and opened up all the deck plates so it could air out. At first I thought that when I filled it it had leaked some into the bilge as it had burped some out of the vent when it got full. Anyway I let it sit for two days with it opened and this afternoon I repeated the process of pulling it forward to get it to drain. Nothing came out of the drain but the smell is still there and there was a small pool in the bilge. Some water but mostly fresh gas. Great!!!! I got my flashlight and a mirror and started looking to see if I could tell where it was coming from. I finally was able to see gas slowly dripping out of the drain on the coffin into the bilge. Great, again!!!! Then I made a discovery, the gasket around the sending unit is leaking. I guess after sitting for a week on the incline enough had drained across the top of the tank down around the foam and then into the bilge. My problem is the tank is full with mixed gas. VRO disconnected. My plan: tomorrow morning  spray the bilge with detergent to get as much out as possible, rinse it out really well, take it to the lake and run the hell out of it so I will have some room to pull the sending unit without having 10 or 20 gallons of uphill gas pour out if I pull it now. I would try to drain some out but all my cans are full. Anybody think this will work or do I need to go get another gas can? Second question: It looks like the gasket is rubber, should I get a cork one or what do you guys think is best?

[wingtime]

Lewis, is it leaking from the gasket under the sender or from around the screws? I noticed on my tank I had to have gaskets under the screw heads. I would try to find a fuel resistant gasket sealer and put that on the screws.  Don't use RTV cause that is corrosive to aluminum over time.

[Capt. Bob]

Second question: It looks like the gasket is rubber, should I get a cork one or what do you guys think is best?

Lewis,
I believe mine is a neoprene type but I'm sure some feel this causes the alum to corrode. You may want to fab a paper one with some gasket sealer if the "rubber" type makes you feel uneasy, corrosion wise.

[seabob4]

Lewis,
Sending units come with a rubberized type of gasket, but it's not neoprene.  We also used this "pipe dope" made by Loctite that was this black, kinda viscous sealant approved for use with gasoline.  You may want to contact Moeller or WEMA and see if they'll sell you a replacement gasket alone.

Another suggestion when it comes to senders.  Things may have changed, but when I was in the business, the machine screws that secure the sender are a real oddball size.  They look like 10-24s, but they're not, and a 10-24 will not thread into the inserts in the tank.  So if you remove your sender, be VERY careful not to drop one of your screws where you can't get it back!!!  And, no, they're not 10-32s either...

[slvrlng]

Thanks guys!

[gran398]

Lew, SB is right, that is a weird little machine screw.

If you do happen to lose one, or need some replacements....there is an old hardware store here in town that's been in biz since 1902. They have them in bronze. They are very old. But never used. They come wrapped in oiled American-made brown paper.

[wingtime]

Probably a 10-28.  When I made my tank I think I tapped the tank for 10-32.    

This is not practical for you but the best thing you could put on there is a sealant used to build aircraft fuel tanks called pro-seal.  It is a two part poly-sulfide that will NEVER leak and is VERY difficult to get off.  Aircraft spruce sells a 3 oz tube of it but it's kinda expensive at $17 and once you mix it the whole thing will harden.  You could skip the gasket and seal the whole sender unit with that but it will hard to get off down the road.  http://www.aircraftspruce.com/catalog/appages/prosealant.php

[seabob4]

Probably a 10-28.  When I made my tank I think I tapped the tank for 10-32.    

This is not practical for you but the best thing you could put on there is a sealant used to build aircraft fuel tanks called pro-seal.  It is a two part poly-sulfide that will NEVER leak and is VERY difficult to get off.  Aircraft spruce sells a 3 oz tube of it but it's kinda expensive at $17 and once you mix it the whole thing will harden.  You could skip the gasket and seal the whole sender unit with that but it will hard to get off down the road.  http://www.aircraftspruce.com/catalog/appages/prosealant.php

Could be a 10-28.  We used 1/4-28s in aerospace, 10s were 10-32s...