Replacing my speedometer pickup what sealant to use

[Rupp]

Guys,
I'm replacing my boats speedometer pickup and I'm wondering what sealant I should use as the old one looks like it was put on with clear silicon. Is that what I should use?

 

[jbcurt00]

Aluminum or fiberglass boat? No silicone on aluminum unless marked as aluminum safe

 

[airshot]

I would never use silicone period, below waterline is even worse. Many better sealants on the market.

 

[Rupp]

It's a fiberglass boat and I'm looking for better sealant recommendations. The silicone was applied at the factory and has worked for 24 years but I'm open to whatever is better.

 

[nola mike]

It's a fiberglass boat and I'm looking for better sealant recommendations. The silicone was applied at the factory and has worked for 24 years but I'm open to whatever is better.

3m 4200 or PL Marine adhesive

 

[04fxdwgi25]

life seal is another good one

 

[dingbat]

Aluminum or fiberglass boat? No silicone on aluminum unless marked as aluminum safe

Never heard of such a thing.
Please elaborate…

 

[Chris1956]

Gee, any sealant that is suitable for below the waterline is fine. I used silicone for 50 years. Pure silicone is completely waterproof.

Silicone is also fine for aluminum. Silicone is often used to caulk windows to siding trim made of aluminum.

Life Seal is good for wet surfaces. If you cannot dry it out, and you need to seal it, Life Seal is the way to go. Water helps with it's curing process.

 

[jbcurt00]

Never heard of such a thing.
Please elaborate…

Most silicone has acetic acid in it to speed/help it's cure.

Acetic acid etches aluminum

EDITTED TO CORRECT CHEMICAL: Acetic not acetate.

 

[dingbat]

Acetate etches aluminum

Are you sure you’re not mixing “chemicals up?

According to all the material comparability charts that I found, acetate has excellent compatibility with aluminum

A goggle search for “Acetate etching aluminum” turns up nothing as well

 

[jbcurt00]

Are you sure you’re not mixing “chemicals up?

According to all the material comparability charts that I found, acetate has excellent compatibility with aluminum

A goggle search for “Acetate etching aluminum” turns up nothing as well

Editted my mistake:

It's acetic acid in some silicone:
Acetic acid in silicone etches the aluminum and leads to corrosion