MagDarter

HELP: Major Holes in Aluminum Boat

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All the major aluminum boat manufacturers use stainless in their boats when they need nuts and bolts or screws.  Why would they do it if it is so bad?

 

And all sheet aluminum boat rot starting at the transom because of it.  I have owned 5 in the last 30 years.  Starcraft seemed to last the longest.  I had that boat for 18 years before the transom needs to be cut out and fixed.  The only good thing about is it's relatively inexpensive to repair.

 

Dom

Edited by Dominic Iadicicco

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Posted (edited) · Report post

Dissimilar metals=corrosion.  This will be expedited in saltwater.  Freshwater will be a slow corrosion but it will happen.  I took a metallurgy class for school and we had to put an aluminum nut on a stainless steel bolt in a glass of saltwater, it took all of a week to mushroom into a glass of muck. 

Edited by Beachbuster

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4 hours ago, Beachbuster said:

Dissimilar metals=corrosion.  This will be expedited in saltwater.  Freshwater will be a slow corrosion but it will happen.  I took a metallurgy class for school and we had to put an aluminum nut on a stainless steel bolt in a glass of saltwater, it took all of a week to mushroom into a glass of muck. 

So plastic washers would be a good solution?  I saw rubber washers exist too but they would dry out in salt water quick right? 

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10 hours ago, MagDarter said:

So plastic washers would be a good solution?  I saw rubber washers exist too but they would dry out in salt water quick right? 

Not quite sure.  I would use all aluminum if at all possible.

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I used azak board sandwiched with sheet aluminum when i redid my transome.  i think something like that is a better solution and never rots.  Mount inside and seal with 5200

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1 hour ago, Captain Ahab said:

I used azak board sandwiched with sheet aluminum when i redid my transome.  i think something like that is a better solution and never rots.  Mount inside and seal with 5200

Is that PVC deck material? 

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Even if you use a plasic or rubber washer you are gonna have metal to metal contact.

 

I have a 1974 aluminum boat with tons of stainless nuts bolts screws etc.  Use in both fresh and salt and the amount of galvantic corrosion is minimal.  Anything below waterline has sealant over it usually silicone or 5200.

 

BUT never ever never use steel on anything. That will cut right through your aluminum hull in short time. 

 

Even dropping a steel part on the hull will do it

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On 6/13/2019 at 3:32 PM, Dominic Iadicicco said:

 

And all sheet aluminum boat rot starting at the transom because of it.  I have owned 5 in the last 30 years.  Starcraft seemed to last the longest.  I had that boat for 18 years before the transom needs to be cut out and fixed.  The only good thing about is it's relatively inexpensive to repair.

 

Dom

What about the Stainless steel motor mount bolts that every manufacturer uses?

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15 hours ago, Stonesipher said:

What about the Stainless steel motor mount bolts that every manufacturer uses?

Unfortunately, they are a problem as well.  This is why leaving an aluminum boat in the water for an extended period of time will cause galvanic corrosion. The less noble metal will always yield to the more noble metal. Now, this is mostly with sheet metal aluminum boats.  Most to these boats are made out of  5052 aluminum less than a 1/8 inch thick.  The plate boats fair much better even with the corrosion. By plate, we are talking 1/4 thick. They are thicker which, makes it harder for the electrolysis process to get through and they are made from alloys that have more magnesium in them which also make them a little more noble in the corrosion ladder.  5086 and 5083.    

 

I hope that helps 

 

Dom

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