Best sealant for unprimed aluminum

[idruthrbfishin]

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.

 

[DaleH]

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.

 

[idruthrbfishin]

[highlight=yellow][/highlight]

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.

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

 

[DaleH]

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

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

 

[idruthrbfishin]

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

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

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.