Make bolted connection watertight?

[donkmeister]

I'm planning to bolt something to the outside of a trailer. I want to make it watertight, so Googled watertight fasteners and it appears they are simply standard nuts and bolts used in conjunction with standard o-rings.

Has anyone had any issues with just rolling your own from the selection of fasteners and o-rings you already have?

[Doofus]

What are you bolting on? Run a bead of silicone round the edge?

[donkmeister]

Just a small bracket, not really anything big enough to use any form of mastic.

[darreni]

PTFE tape or blue hylomar.

[E-bmw]

I am assuming that as you are bolting a bracket on and asking about watertight fittings, you don't want water getting into where it could allow rust to get a hold.

That being the case you need to stop water getting between the bracket & the trailer and between the nut/bolt & bracket.

I would have thought the best way to do that would be similar to above but use a polyurethane sealant rather than silicone as it never truly sets and remains flexible, that is what is used on caravans/motorhomes rather than silicone which doesn't really stick properly.

[s p a c e m a n]

Honestly you can't beat running a little bead of sikaflex around the bolt, nipping it up a bit and then doing it up tight once it's cured. That's coming from someone with a stupid fibreglass car that was kept outside for years