Out board Gear box bung screw, Stainless 316?

[mick.j]

Hello all.

I just wish to ask any outboard experts out there about the metal used in the Gear box bung plug in outboards, I presume it's made solid 316 stainless ?

Or could it be some other fancy made screw , say made of Monel or another mix of metals that don't cause reactions

in theory if it is Stainless going into cast there will be a reaction due to dissimilar metals (stainless) could eat away at the cast, but I presume the surface area of the thread of stainless that touches the cast is neutralized due to anodised installed on the leg and the fact small amount of stainless in a large amount of cast is ok, rather than a large amount of stainless and a small amount of dissimilar metal (cast).

I wish to double check. I have tried to contact my local dealer but they are unwilling due to possible liability strange, but anyway maybe they just didn't really know.

[Noelm]

Never seen a rusty one, so my guess is stainless.

[552Evo]

See if the screws magnetic. Stainless won’t have much effect with a magnet.


Saltwater fishing, boat mad but has a job that gets in the way.

[tunaticer]

See if the screws magnetic. Stainless won’t have much effect with a magnet.


Saltwater fishing, boat mad but has a job that gets in the way.
Entirely incorrect, there are dozens of grades of magnetic stainless steel.
The drain plug should be 316 stainless steel.

Corrosion is not an issue because the seal is at the head of the bolt, the thread is in contact with oil, not water.

[552Evo]

Entirely incorrect, there are dozens of grades of magnetic stainless steel.
The drain plug should be 316 stainless steel.

Corrosion is not an issue because the seal is at the head of the bolt, the thread is in contact with oil, not water.

So is 316 magnetic ?


Saltwater fishing, boat mad but has a job that gets in the way.

[Noelm]

316 is ever so slightly magnetic, so I guess in a way the answer is no (kind of)

[mick.j]

Thanks jack the bung plug I have is M10 1.25 fine thread but over the years of dumping oil and constantly buying the new washer I wish to find a better way, I found using a thicker nylon washer is perfect but it limits the thread length to fasten.
( new nylon washer is 2ml thick, standard washer is very thin and can sometime pinch and distort )
Genuine bung bolt is only 8 ml long.

searching for an M10 1.25 thread in a stainless 316 button head is not easy, what makes it even harder is I was hoping to get it in a button head Allen key socket.
thankyou again

[gazza2006au]

I have seen them made from aluminium and stainless steel, Mick these days u can get anything made just find someone with a lathe and they willspin one up for u

[mick.j]

thanks Gazza thats a great idea. I know just the person :bulb2::bulb2: Its actually right in front of my face. My next door neighbour does all that metal work.

[gazza2006au]

If your neighbour has a mill a added bonus he/she can machine whatever head u want on the screw