Best sealant for unprimed aluminum

Re-skinning transom. What is the best sealant for unprimed aluminum (UPA) below the waterline? Have read that 5200 attacks UPA. Was strongly considering butyl tape. Seems like a decent choice, convenient to use, not so messy, stays flexible, etc.

I believe StarCraft recommends that tape. I have the exact tape StarCraft recommends listed in the rebuild of my StarCraft 16’ transom, per my signature.

However, I myself would never use anything next to UNprimed aluminum. But I do boat in saltwater. And I’m lucky, I still have access a 2-part epoxy zinc-chromate primer.

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DaleH said:

I believe StarCraft recommends that tape. I have the exact tape StarCraft recommends listed in the rebuild of my StarCraft 16’ transom, per my signature.

However, I myself would never use anything next to UNprimed aluminum. But I do boat in saltwater. And I’m lucky, I still have access a 2-part epoxy zinc-chromate primer.

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[highlight=yellow]Dale, so you would suggest using a self-etching primer prior to applying the butyl tape?[/highlight]

idruthrbfishin said:

[highlight=yellow]Dale, so you would suggest using a self-etching primer prior to applying the butyl tape?[/highlight]

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I would prime any pieces bonded or otherwise placed adjacent to each other.

DaleH said:

idruthrbfishin said:

[highlight=yellow]Dale, so you would suggest using a self-etching primer prior to applying the butyl tape?[/highlight]

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I would prime any pieces bonded or otherwise placed adjacent to each other.

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Hey Dale, finished up the transom on my Grumman. It is worth noting, that the factory did not prime the bare aluminum before applying the butyl tape. This boat is a 1986 and the seams themselves are actually in very good condition, which surprised me given the extremely poor condition of the transom. I also was surprised to see how many fasteners of dissimilar metals were used on the aluminum. Steel, stainless steel. no isolating agents whatsoever.