through-hull sealant

[greenghost45]

Hello;
I recently pulled the raw water pump through-hull because it was turning and pointing the wrong way, in my Ranger 21EC. Probably as a result of me replacing the ball valve that serves that through-hull. What sort of sealant is recommended before reinstalling it? Sikaflex? Silicone?

Thanks!
David

 

[FlyMeAway]

Definitely not silicone. You want an adhesive-sealant; silicone is just a sealant. Using silicone on a thru-hull is a great way to end up with a very expensive mooring anchor for your next boat.

Thru-hulls should be sealed with 3M 5200 or comparable Sikaflex (though extensive experience with sailboat thru-hulls says 5200 or bust).

You can also use 3M 4000-series below the waterline. Most of the DIY sailors I know wouldn't do that, even though it is (usually) a bit cheaper. The primary advantage of 4000 is that it is a bit easier to remove than 5200, but thru-hulls are not generally supposed to be "removable".

 

[HookedUp]

I've not done a thru-hull and I probably would use 5200 there. It is possible to 'remove' but very difficult. This product helps in removal https://store.marinebeam.com/brands/Un%2dHesive.html.

I've used 4200 on trim tab screws, transom mount transducers, etc. It's is 'almost' like 5200, but you can still remove the screw. With 5200 it would be almost impossible.

 

[Ralf H]

Hi David,

Here at the factory, we use Sikaflex 291. But as others here have already mentioned, if that's not readily accessible, you can use 3M 5200. Just be aware that you'll need a jackhammer if you ever need to take it off again 😉

Cheers,

Ralf

 

[knotflying]

Not quite sure I would use 5200, if anything 4200. It is a rather permanent installation and if you want to ever replace things it will not be fun. I would use Life Seal or Life Caulk. I have always used that for underwater sealing and never had an issue.

 

[FlyMeAway]

Not quite sure I would use 5200, if anything 4200. It is a rather permanent installation and if you want to ever replace things it will not be fun. I would use Life Seal or Life Caulk. I have always used that for underwater sealing and never had an issue.

A sealant is different than an adhesive sealant. Using life seal or life caulk on a thru-hill is asking for a sink boat.

Re: the comments on 5200: it is hard to remove. Which is exactly why you should use it for thru-hulls!