Thru Hull hardware sealing

Hi All,

One of the finds yesterday during the haul out was some badly corroded and probably leaking bolts from the swim platform. What sealant is best to use with all the new SS hardware? 4200, 5200. Boat will be out of the water for a week.

Dave

5200 below the waterline, 4000 above is what I use. Been doing it for decades and had good luck.

4000 has better UV properties.

4200 for fittings above and below. 5200 if you want to cuss and swear a lot when you inevitably have to remove the fitting. 4000 for caulking around windows and such.

Sikaflex 291!

dwhatty, you are so right about 5200.

Tom.B said:

Sikaflex 291!

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For windows or any other things you want to be watertight above the waterline +1 for Sikaflex 291. I use 291 LOT for windows trim as it allows you time to setup everything.

If you want to seal something but keep it removable if needed, 4200 is good.
If you want to seal something hard, solid, unmovable and rock solid 5200 is the one.

Each one has its usage.

L.

Lou_tribal said:

For windows or any other things you want to be watertight above the waterline +1 for Sikaflex 291. I use 291 LOT for windows trim as it allows you time to setup everything.

If you want to seal something but keep it removable if needed, 4200 is good.
If you want to seal something hard, solid, unmovable and rock solid 5200 is the one.

Each one has its usage.

L.

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I have used it for all the thru-hull I have added (of course... that doesn't really PROVE anything, but they are still holding well after two years). Anyway, it is my opinion that there is little need to bond something like a thru-hull so tight that it takes a Sherman tank to get it loose. Thru hulls need replacing every now and then and having it be removable is a better way to go.


Sikaflex®-291

Sikaflex®-291 is a 1-component, marine grade polyurethane elastomeric adhesive and sealant. Used by many boat builders, its fast cure time makes it ideal for applications where speed is important.
Use

General all-purpose, marine adhesive and sealant, which may be used for light duty bonding. Sikaflex®-291 has excellent adhesion to gelcoat, fiberglass, metal and wood that can be gunned or brushed into place.
Characteristics and Advantages

• Use above and below water line Resists salt water
• Fast strength build-up
• Paintable and sandable
• Excellent bond
• NSF approved for potable water (black and white only)
• USDA approved for incidental food contact

Color

White and Black

Dave_E said:

Hi All,

One of the finds yesterday during the haul out was some badly corroded and probably leaking bolts from the swim platform. What sealant is best to use with all the new SS hardware? 4200, 5200. Boat will be out of the water for a week.

Dave

Click to expand...

Your problem is probably in the hardware, not the sealant.
Silicone Bronze fasteners should be used in underwater applications.
Hope your transom is not cored!

Real men use 5200. Girly men use 4200.
Kapnd (spell corrected to "lap dance") is right. I bet your fasteners are 304 stainless. Switch to bronze or at least type 316 stainless.

5200 is a glue that seals.

AS all sealants fail in time one that is easy to remove and replace is the least amount of work over time.

To install a seacock 5200 might be OK, but for the thru hull screwed into the seacock Dolphinite is easy to work with.

Ports , hatches ,windows, deck hardware all are easier to R&R with non glue.

Most of the dissolving decks on TT seem to come from leaks at fittings , that are not on a PM list for sealant R&R.

Ditto the cautions on 5200. It's permanent. I made the mistake of installing a depth transducer with it, the transducer failed and had to be replaced. What a fight to remove it! Never again! I installed the replacment and bedded it with a lot of polysulfide (Life-Caulk). Won't harden, cures underwater, and isn't an adhesive. An adhesive isn't really required for a thru-hull, it's a mechanical attachment, so it only needs to be sealed. Polysulfide is an excellent sealer, but can be removed if needed.

Maerin said:

Ditto the cautions on 5200. It's permanent. I made the mistake of installing a depth transducer with it, the transducer failed and had to be replaced. What a fight to remove it! Never again! I installed the replacment and bedded it with a lot of polysulfide (Life-Caulk). Won't harden, cures underwater, and isn't an adhesive. An adhesive isn't really required for a thru-hull, it's a mechanical attachment, so it only needs to be sealed. Polysulfide is an excellent sealer, but can be removed if needed.

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That, sir, is an excellent point.