Re: Newbie Questions Restoring 1957 Johnson 18hp FDE-11

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Mumbles


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#68541

Expanding on the primer/activator usage a bit, it’s true, the anaerobic sealers won’t cure on certain metals. Pure aluminum being one of them. Since outboard castings are alloys containing trace amounts of other metals for strength and corrosion resistance, the sealer will cure without using the primer/activator as long as the surfaces are perfectly clean down to bare metal. I’ve been told before that it’s the copper content in the aluminum which activates the anaerobic sealer. The primer/surfacer is copper based and that’s how it works. I guess what I’m saying is if you have it, use it. If not, don’t lose any sleep over it as long as the metal has been thoroughly cleaned.

The alloys used have changed over the years and early motors may have used a more pure form of aluminum, making the use of the activator necessary. Today, Mercury Marine even claims their aluminum alloy contains 10 – 20 times less copper than their competitors products. Depending on what other metals are added to the MercAlloy, using the primer/activator might be mandatory when sealing up a newer Merc.

https://www.mercurymarine.com/en/us/leg … ry/week30/

Here’s a list of metals straight from Permatex showing whether the primer/activator needs to be used or not.


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