galvanic corrosion

[alwayslookin]

I am putting together the transom on A 17" bluefin. The question I have is will a fiber gasket behind the bolt heads and washers help eliminate the corrosion as this boat will see mostly saltwater use? I am sealing all through hull fasteners with 5200 as I am putting it together, was just thinking the gasket may help. Any/all input is greatly appreciated. Thanks all

 

[DaleH]

Sure it will! Anything non-metallic to insulate the SS from the aluminum will work.

 

[Pappy]

But - To fully insulate the through bolts you would also need a non-conductive bushing. Your idea will help though.

 

[Al U Minium]

I have used 5200 to coat the bolts, washers, nuts, the hole they go through, clothes, me, tools. When you have torqued the bolts, wipe off the excess 5200 and you will be good for years, Do not use fiber washers, nylon, etc. The bolt up fasteners will always move even if it is just from thermal expansion and contraction. The 5200 provides the barrier that will stay in place.

 

[mbweimar]

The gasket most likely won't withstand the compression of the engine bolt. I used regular automotive silicone on my boat, and after 3 years of saltwater use I pulled the engine and all was fine.

 

[Molokai]

I was thinking of doing this same thing using some hypalon patching material i had laying around. That stuff is really durable.

 

[DaleH]

But - To fully insulate the through bolts you would also need a non-conductive bushing. Your idea will help though.

I've put adhesive-lined heatshrink over bolts with good success, although crevice corrosion will still occur.

The gasket most likely won't withstand the compression of the engine bolt. I used regular automotive silicone on my boat, and after 3 years of saltwater use I pulled the engine and all was fine.

FYI, most regular silicones are made with acetic acid, which attacks aluminum.

 

[alwayslookin]

well, I'm gonna do it! I have a 12"x24" piece of 1/16" gasket material going to use a 30-30 shell to cut the inside hole and a piece of 1/2 tubbing sharpened with a file to cut the outside diameter. For the other odd shaped things just trace an outline and get out the razor blade. Just gotta get it done in all my spare time. HEHE

 

[DaleH]

Believe me, I have even used DUCT TAPE as an insulating material to prevent GC where SS hardware was used on a tin boat and good ol' duct tape works! Not pretty years later ... when I took it apart, but the parent material (properly prepped and primed of course) was still integral with ZERO corrosion issues.

FWIW, https://www.clipsandfasteners.com/Nylon_Flat_s/211.htm sells nylon washers in bulk in all diameters and thicknesses. When I re-did my complete new transom (new tin skins AND new core) the OEM Starcraft methodology had used 32 SS bolts, IIRC, tying the rear skin to the splashwell and inside skin. Using the nylon washers with the bodies and bearing surfaces coated with Tef-Gel sure made it protected (against corrosion) and FAST work!

 

[Pappy]

Dale - That adhesive backed heat shrink is one Hell of a good idea along with non conductive washers...thanks!

 

[Buckethead]

I used nylon washers with SS hardware and 5200. Used a little extra 5200, ran the nuts down to the point where the nylon was just starting to flatten the 5200. Let 'er cure for a week before you tighten them down and should be bulletproof. I did my transom in late 2012-early 2013, no troubles to date.