Corroded Bolts in Aluminum

Boatdood

Seaman Apprentice
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Aug 22, 2008
Messages
43
Re: Corroded Bolts in Aluminum

Lots of heat suggestions here but I had a saying that worked for me for many years. Heat 'em and beat 'em. If you can get to the area surrounding the bolt threads where it's frozen beat on it. Use a hammer, or a hammer with a punch, whatever it takes to rap it. The idea is to break up the corrosion and the hold it has on the bolt shank and threads. I've found that the beating it method sometimes works when the heating it method fails, and a combination of the two approaches may work the best.
 

Bear 45/70

Seaman
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Nov 2, 2008
Messages
59
Re: Corroded Bolts in Aluminum

The fasteners should already be SS ... I've never seen anything else.

First off, most fastners in O/Bs and especially older O/Bs are not stainless.

Secondly, most stainless bolts are softer than a steel bolt and will break easier.
 

asdasc

Senior Chief Petty Officer
Joined
Aug 28, 2008
Messages
680
Re: Corroded Bolts in Aluminum

I have questions! (big surprise)

I thought that the goal of heating it was to get it to expand and loosen it's grip on the bolt, so anything I have tried this on involved keeping the bolt cool and heating the housing. As you can imagine, since Aluminum conducts heat so well, this is almost impossible.

So you guys heat the bolt?!?! Gosh, I wish I had known that...
 

Grem

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Joined
Oct 6, 2008
Messages
45
Re: Corroded Bolts in Aluminum

The heat disrupts the 'salts' formed on the screw threads due to galvanic corrosion as well as the differential expansion tending to assist breaking the bond.
 

HybridMX6

Senior Chief Petty Officer
Joined
Oct 22, 2008
Messages
676
Re: Corroded Bolts in Aluminum

Well, the score is propane torch 1, broken bolt 0.
I did what Boatdood was suggesting, heat it and beat it. My particular bolt was the one in the midsection, right above the trim tab. I was pulling the lower unit and this bolt snapped on me instantly, no warning, barely even got the socket on it. It only snapped the head off, so once the lower unit was removed it had plently of shaft length to get ahold of with some vice grips. I used a propane torch, kept steady heat on it, and every minute or so I'd give it a few good thumps with the vice grips, either side to side or just directly on the bottom of the bolt (where the head used to be before it snapped). Did that for about 5 mins, locked the vice grips on, and although it was a bit stiff, it did come out without needing anything more than the vice grips. I had a 2' steel bar for a breaker bar if I needed it, but I didn't.
Just wanted to pass on the info in case others are keeping an eye on this thread also.
And thanks to those who replied to the original posters' problem, it helped me.
 

Bear 45/70

Seaman
Joined
Nov 2, 2008
Messages
59
Re: Corroded Bolts in Aluminum

I have found that heating the bolt to red hot glowing, then letting is cool works sometimes. But you have to replace the bolt because you destroyed it's temper.
 

samo_ott

Vice Admiral
Joined
Jun 18, 2006
Messages
5,125
Re: Corroded Bolts in Aluminum

Interesting. I always heat the aluminum housing around the bolt as it will expand and don't heat the bolt at all (although it gets it indirectly) and it usually works. I guess everyone does it differently just like trying to free up stuck pistons! :)
 

Bear 45/70

Seaman
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Messages
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Re: Corroded Bolts in Aluminum

Interesting. I always heat the aluminum housing around the bolt as it will expand and don't heat the bolt at all (although it gets it indirectly) and it usually works. I guess everyone does it differently just like trying to free up stuck pistons! :)

The guy that showed me the red hot bolt trick had a machine shop and almost all he dealt with was outboards, sterndrives and inboards. Usually by the time he got them, everything else had been tried. He did have an EDM machine for the broke off even with the surface bolts in non-replaceable castings.
 

samo_ott

Vice Admiral
Joined
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5,125
Re: Corroded Bolts in Aluminum

My concern would be that after the bolt was heated up red hot and then cooled that it would lose its temper and then the rest of it would snap off even easier if you tried it with vise grips etc.
 

Bear 45/70

Seaman
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Nov 2, 2008
Messages
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Re: Corroded Bolts in Aluminum

My concern would be that after the bolt was heated up red hot and then cooled that it would lose its temper and then the rest of it would snap off even easier if you tried it with vise grips etc.

Gee, I do believe I said that when I brooched the super hot issue.

"But you have to replace the bolt because you destroyed it's temper."
 

samo_ott

Vice Admiral
Joined
Jun 18, 2006
Messages
5,125
Re: Corroded Bolts in Aluminum

Gee, I do believe I said that when I brooched the super hot issue.

"But you have to replace the bolt because you destroyed it's temper."

I thought that was kind of obvious? If you're trying to remove the bolt it's because it's already busted and it has to be replaced whether you heat it or not! :)
 

asdasc

Senior Chief Petty Officer
Joined
Aug 28, 2008
Messages
680
Re: Corroded Bolts in Aluminum

I heard of a new trick recently that seems to work. Heat up the bolt hot, then take a birthday cake candle and hold it where the bolt and casing meet. The heat melts the wax, which is now thinner then water and capilary action sucks it down into the threads. There it acts like a good lubricant and helps the bolt break free and you can screw it out.
 

nymack66

Petty Officer 1st Class
Joined
Aug 5, 2009
Messages
356
Re: Corroded Bolts in Aluminum

Mix in a bottle 50/50 mix of Diesel and Kerosene, heat the bolt not red hot for sure then soak with the mixture be careful not to burn or start a fire, the heated metal will suck the mixture in to the tread, next step is use breaker bar to break it free then switch to a impact driver and rock it back and forth soak generously as you go..
Your patience will be the end results if you ended up broken bolts or not ... Just think of the drilling part as hell ...
 

samo_ott

Vice Admiral
Joined
Jun 18, 2006
Messages
5,125
Re: Corroded Bolts in Aluminum

I heard of a new trick recently that seems to work. Heat up the bolt hot, then take a birthday cake candle and hold it where the bolt and casing meet. The heat melts the wax, which is now thinner then water and capilary action sucks it down into the threads. There it acts like a good lubricant and helps the bolt break free and you can screw it out.

Hey. You resurrected 14 month old thread! But that's an interesting idea using wax but are you sure it's thinner than water?
 

asdasc

Senior Chief Petty Officer
Joined
Aug 28, 2008
Messages
680
Re: Corroded Bolts in Aluminum

Yeah, I never did get that bolt out. It is out at the island, as soon as I can get back out there, I will try this. I heard about it on another forum for my Opel GT. Everything old has this common issue it seems. :)
 
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