Rust from Motor Bracket Bolt

[TomS]

At the end of last year I noticed that one of the motor mounting bolts was 'sweating' a bit of rusty colored water. I'm assuming that water has gotten in behind the sealant and is causing the bolt to rust from within, which means that water is also potentially getting into my transom.

My plan is to see if I can remove the bolt, investigate the condition of the surrounding transom for signs of water intrusion/rot and then replace the bolt and re-sealing it.

Anyone else have to do this before? Anything I should be looking for?

-- Tom

 

[passingwindII]

that bolt apears to me as a galvanized bolt, pull it out check transom hole, replace with 4200/5200 marine caulking and a stainless bolt washer nut. gl

 

[DaleH]

While the picture does make it look like a galvy fastener, note that a 'cheap' grade of SS hardware could do that under certain circumstances. Note that ANY piece of stainless steel (even premium grades) are ALL subject to advanced corrosion when placed under high stress. This is called 'stress or crevise corrosion". But to me, that much staining must be coming from a steel source, so I'd bet a suspect bolt too.

Taking the bolt out and picking at the ID of the hole with a large needle or icepick will tell you if the wood is wet or punky. I have some extremely thin (as water) 2-part epoxy we could weep into the hole with a syringe just to seal once and for good.

Call me ... I'll make the housecall, then can give you the $$ I owe Gas Money Graphics for the CC logo design.

 

[TomS]

Thanks guys, looks like I'm on the right track.

I have some penetrating epoxy leftover from a previous project that I think I can use. Its funny, but the other end of the bolt, which is on the outside of the transom, looks perfect, no rust or signs of corrosion - just like the other three. They all look spotless, so I'm assuming (hoping) they may have just picked up a galvanized or lower quality washer by accident during the install.

-- Tom

 

[DaleH]

"If" it is a SS bolt, albeit a poor quality one, the prime reason it corroded, and that the outside didn't, would most likely be the moisture-laden environment down in the bilge area there.

With a less clean atmosphere and sufficient O2 to 'blanket' the SS fastener, the SS would have lost it's protection from the elements. In metalurgy circles they actually have a term for this - called 'oxygen deprivation induced corrosion'.

 

[Lucky John]

Looks like it may not be a stainless washer to me.Head looks good,most of the nasty ooze looks like it's coming from the washer.