Advice: Random holes/plugs in topside of aluminum hull. What are they? How to repair?

[mlt2819]

Hi,

I bought a late 70s aluminum yacht last autumn and I'm in the process of making a few improvements to it. Running along the top edge of the hull (just below the toe rail) was a 6 inch strip of epoxy paint. There was a bit of corrosion underneath a few sections of the paint (which had bubbled up), so I've removed the entire strip. Aside from applying a protective coating of Alumetron, I'm planning to keep it bare from the waterline up. However, when I removed the paint I saw that there are multiple plugs/holes about 5mm in diameter (see attached photo) running 1-2 inches below the toe rail/top edge of the boat (not in any particular order/spacing either). It's my first boat, so I've got a lot to learn... can anybody explain what they are? I guess it's something that was necessary for the assembly/welding process of the boat... or is it structural? There's a couple of dozen of these on both sides of the boat and maybe 1/3 - 1/2 are filled up with what looks like white oxide paste from corrosion (which I can scrape it out easily). The rest look fine.

How should I repair and fill these holes? I'm guessing the first thing is to scrape out the paste, sand the holes with some light grit aluminum oxide paper, passivate the area (I'll use Marine Grade Alumabrite), clean/degrease the area and then fill it with a Durafix (or similar) welding rod?

Any info/input/wisdom would be greatly appreciated!

Thanks

https://ibb.co/9Y3hMfq
https://ibb.co/SdCfxwL

[mcarthur]

Re: Alumetron, we were going with Cerakote clear on the aluminium. Any reason you chose alumetron?

[coopec43]

I bought a late 70s aluminum yacht last autumn
Do you know the yacht design or is it a "one-off? I'm wondering if you can work out what the holes were for?