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Capt.Zula 04-01-2010 11:31

What Gasket Material for Diesel Tank Inspection Port ?
I am new to this forum and recently cut inspection ports into my aluminum fuel tanks. I had aluminum plates fabricated but not sure what material to use as a gasket. Rubber comes to mind, but not sure if rubber with work with the new diesel formulations. What have others used?

cdennyb 04-01-2010 12:11

TRY TO GET AHOLD OF SOME "EPDM rubber". It's pretty impervious to any fuel and/or additives. My second choice would be a sheet of Viton/Buna-N but it'd be pretty pricey. The EPDM should cost about $18.00/sq ft in a .100 thickness.
Mcmaster Carr has some
Buna-N Material in sheet form: PN#1890T14 12" x 12" x 1/8" $23.00
epdm sheet: PN#8985K44 12" x 12" x 1/8" $18.15

OH, welcome to the board. It'll be fun.

gonesail 04-01-2010 12:52

what he said: nitrile rubber or Buna-N

S/V Antares 04-01-2010 13:08

Also Be sure to use fiber washers on the flange bolts or better yet if you have blind fasteners (The screws do not enter the tank) as diesel will find its way out and smell. At least goop them (The screws) up with a non hardening fuel approved sealer when installing the plate. Auto part store stuff, easy to find. If you are in Guatemala as your location notes do not let anyone talk you into using an old innertube as a gasket. Hold out for the real thing (Buna/Nitrile). BTDT

RAMGas10 24-09-2010 06:23

Nitrile Rubber
I do not believe that EPDM rubber is the best to use with fuel, and viton is a very expensive material.

Nitrile is the cheapest material that will do the job. You want a sheet of nitrile gasket material.

Over and out,


Christian Van H 24-09-2010 06:57


Originally Posted by gonesail (Post 383242)
what he said: nitrile rubber or Buna-N

This is exactly correct. has it if you can't find it cheaper...

ShipShape 24-09-2010 07:14

1 Attachment(s)
Although diesel fuel is an "oil", it is also an interesting solvent, and this is one item you need to forget about the price and get the correct product: Buna-N.

This summer replacing the 27-year old fuel fill and vent hoses finally made it to the top of The List. I wanted to have the tanks empty for that, and when I removed the first inspection hatch - ooooh - some #%*@ dimwit had used a diesel-soluble gasket material, which was in the process of merrily dissolving. Quite a few gooy soft chunks fell into the fuel when I pulled off the cap. To say that cleaning up that nasty mess was a PIA is a tad of an understatement.

It is hard to find, I got mine from from McMaster-Carr. Since my tanks are fiberglass I went with 3/16" to insure that they would completely conform to the rough, uneven surface. If your tank's port is smooth and even probably 1/16" is sufficient.

The Buna-N cuts easily with scissors, but you will need a punch to make the bolt holes (also available at MMC). I made my bolt holes a little bit larger than the bolts. Also, since the bolt holes are not uniformly spaced I left one of the corners on to mark the orientation of how the gasket fits on the tank.

Attachment 19556

Chief Engineer 24-09-2010 20:29

I just love smart people....good idea!!!!!!!!!!!!!

sww914 24-09-2010 23:01


Originally Posted by Chief Engineer (Post 527639)
I just love smart people....good idea!!!!!!!!!!!!!

Thanks for sharing that good idea. I will use it and look smart too.
Of course, I will lie and say I thought of it myself. :)

never monday 25-09-2010 04:17

5200 or

work well with Aluminum also

ShipShape 25-09-2010 05:10

Dude! You're gonna have a lot of Mondays with 'solutions' like that. 5200?! Of course I could be wrong, but I think Capt.Zula cut inspection ports into his tank because he would like to look inside his tanks more than once. :D

As for the Gasket Maker, that would be great if you could give it a try and let us know if it is diesel-soluble or not. :devil:

GordMay 25-09-2010 05:25


Originally Posted by ShipShape (Post 527751)
Dude! You're gonna have a lot of Mondays with 'solutions' like that. 5200?! Of course I could be wrong ...

Indeed dude, you could be wrong.

Pat probably expects we’ll lay a bead of 5200 on one part only (tank OR port cover), let it cure fully , and only then mate the parts, closing the tank.

However, diesel fuel softens and damages polyurethane adhesive sealants, such as Sikaflex 296 and 3M 5200.

Polysulfide (Thiokol) sealants, such as 3M “101" or Boatlife “Life Calk”, are most often used in conjunction with diesel & gasoline fuel systems.

See also ➥

rusky 25-09-2010 05:35

A year ago, I had to redo mine and only had what was at hand which was neoprene rubber and loctite. 12/12 on and it looks good. Can you guys who know what you are doing, tell me if this combo on a ss tank is OK?

ShipShape 25-09-2010 09:43

ABYC Standard 33.18.1 for diesel fuel tanks:

"All materials used shall be resistant to deterioration as a result of contact with diesel fuel and other liquids or compounds with which the material may normally come in contact under normal operating conditions, e.g., grease, lubrication oil, common bilge solvents, and salt or fresh water."

Buna-N meets this standard.

In the "Findings and Recommendations" section of a survey report, fuel system deficiencies are usually reported under "Safety Deficiencies and Federal Violations". If you are using a gasket material that does not conform to the ABYC standard, in the event of a fuel mishap it is likely that your insurance company will find you negligent and will not cover you.

GordMay 25-09-2010 10:20

My original post (#12) was poorly composed, for which I apologise.
I replied to ShipShape’s apparent objection to polyurethane, being it’s incredible tenacity (stated post #11); and under emphasised the true objection to 3M “5200" (in this application), being it’s incompatibility with fuel.
ShipShape’s post #14 is absolutely accurate (IMO).

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