Best sealant for unprimed aluminum

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idruthrbfishin
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Best sealant for unprimed aluminum

Post by 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.
transom1.jpg
transom2.jpg
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HVAC mechanic in NEPA for 25+ yrs.
1998 Crestliner w/ 2001 2 stroke 60/40 Merc Jet
1986 16' Grumman Skidaddle w/ 60 HP Evinrude
1955 14' Viohull
1958? 12' LoneStar

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DaleH
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Best sealant for unprimed aluminum

Post by 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.

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idruthrbfishin
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Best sealant for unprimed aluminum

Post by idruthrbfishin »

DaleH wrote: 20 Jul 2021, 21:52 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.
Dale, so you would suggest using a self-etching primer prior to applying the butyl tape?
HVAC mechanic in NEPA for 25+ yrs.
1998 Crestliner w/ 2001 2 stroke 60/40 Merc Jet
1986 16' Grumman Skidaddle w/ 60 HP Evinrude
1955 14' Viohull
1958? 12' LoneStar

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DaleH
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Best sealant for unprimed aluminum

Post by DaleH »

idruthrbfishin wrote: 21 Jul 2021, 09:51 Dale, so you would suggest using a self-etching primer prior to applying the butyl tape?
I would prime any pieces bonded or otherwise placed adjacent to each other.

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idruthrbfishin
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Joined: 20 Nov 2018, 12:17
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Best sealant for unprimed aluminum

Post by idruthrbfishin »

DaleH wrote: 21 Jul 2021, 12:03
idruthrbfishin wrote: 21 Jul 2021, 09:51 Dale, so you would suggest using a self-etching primer prior to applying the butyl tape?
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.
HVAC mechanic in NEPA for 25+ yrs.
1998 Crestliner w/ 2001 2 stroke 60/40 Merc Jet
1986 16' Grumman Skidaddle w/ 60 HP Evinrude
1955 14' Viohull
1958? 12' LoneStar