Cadillac Alumimum Boat Restoration

eprigge

Recruit
Joined
Jun 22, 2012
Messages
2
I've got an old Cadillac boat that I need to fix up and I think I need some guidance on what to do from the wise people here.

Here she is (Cadillac Model 112):

IMG_3908.jpg

IMG_3910.jpg


Overall, it's in very good condition, no leaks, mild surface corrosion. The main problems are that the transom/motor mount wood is finally coming apart and severe corrosion in spots where steel fittings had been used for assembly. I will make the wood parts but I need help with the corrosion issues. It was (and will hopefully be again) a salt water boat.

The wood parts and aluminum castings in the rear were all attached with some kind of steel bolts and they had corroded to the point of having to be drilled out. Problem is, where steel bolts faced on aluminum, here's what's left:

IMG_3913.jpg


Not good. I'm thinking of cutting out the affected areas until I'm into good metal and then TIG weld in plates to rebuild. Would anyone know what alloy aluminum this boat was made of, or at least what alloy would be compatible with the existing metal?

As to the castings, I'm thinking of bead blasting & polishing them. Maybe anodizing afterwards for protection. It'd be nice if I knew what alloy they were as to whether anodizing would work. They are much worse off than the extruded aluminum but still structurally sound:

IMG_3917.jpg


The blooms of surface corrosion on the hull aren't that bad (as you can see in pictures above) but I'd like to be able to get it looking as new. I was thinking of some kind of blasting/abrasive process to get a nice uniform corrosion free surface. I assume these boats are anodized though, right? So, I don't know if removing the surface corrosion would be worth the loss of whatever anodizing is left. Not sure what to do.

Finally, once I'm re-assembling, what sort of hardware should I use to prevent corrosion? I thought good stainless would work but I've read that it will cause problems... so that leaves aluminum plated hardware or?

Any suggestions are very much appreciated!
 

jigngrub

Fleet Admiral
Joined
Mar 19, 2011
Messages
8,155
Re: Cadillac Alumimum Boat Restoration

Your hull material is more than likely 5052 marine alloy aluminum, I doubt that it's anodized. Cutting out the bad and putting new back is the best fix.

Stainless steel hardware is fine to use. go look at new aluminum boats and checkout all the stainless fasteners they use at the factory. Everything from motor mounting bolts to deck screws and mounting hardware is SS.

400 grit sandpaper followed by Mothers aluminum polish applied with an orbital buffer will make your boat shine like new.
 

greenbush future

Lieutenant Commander
Joined
Aug 28, 2009
Messages
1,814
Re: Cadillac Alumimum Boat Restoration

Dang that rust spot almost looks like the boat was made out of galvanized steel. Any idea what caused that to happen?
 

64osby

Admiral
Joined
Jul 28, 2009
Messages
6,799
Re: Cadillac Alumimum Boat Restoration

Saltwater, Steel and Alum. don't mix as your boat proves. Cut out the really bad areas, sand off any other corrosion, wash with vinegar and water, rinse and weld in patches.

On the end caps, I wouldn't worry about anodizing, There is a product called Shark Hide, but is would be expensive if your just using it for the end caps. Maybe look at some Alum wheel (auto) polish.
 

eprigge

Recruit
Joined
Jun 22, 2012
Messages
2
Re: Cadillac Alumimum Boat Restoration

Thanks for all the info guys. It's especially useful to know that it wasn't anodized in the first place and the repair alloy, that opens up my refinishing options. I guess I'll go with 316 stainless hardware unless I can find some aluminum hardware.

greenbush future: the rust spots are from the steel hardware that used to hold everything together. It's amazing what salt water does to steel...
 

64osby

Admiral
Joined
Jul 28, 2009
Messages
6,799
Re: Cadillac Alumimum Boat Restoration

Alum hardware as no strength, it will bend and stretch with any tension or force compared to stainless. Stainless is the way to go unless your using rivets.
 
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