Best Sealant For Hull Penetrations

[Fishinguy40]

I am going to remount the swim ladder on the back of my boat. The boat is 18.5' aluminum Monarch. I'm doing this because I susect the penetrations on the transom have been leaking some. I've already remthe bolts and ladder, cleaned the hull thoroughly and let it dry foe several days. I'm just wondering what is the best sealant to use around the bolts and washers. 100% silicone or is there something better?

[Fishinguy40]

Wow!

I thought this would be an easy one.

[Jim Almquist]

When ever I have put holes through the hull I have just used marine grade silicone. It is kinda spendy but the stuff holds great.

[311Hemi]

Marine grade silicon or 3M 4200 adhesive sealant, although your not really trying to stick anything to the hull. Should be fine with the marine grade silicon, that's what they use for mounting engines. I would just double check it says it's for use below the water line.

[walleyemaniac]

+1 marine grade silicone. Stuff works great, took my transom apart to replace the wood, sealed everything up with that silicone when I put it back together. Hasn't leaked a drop yet. (2 1/2 years)

[Transporter]

If you want a permanent water tight seal, there are two types of caulk that are better than silicone. One is 3M 5200, which is the strongest bonding caulk I know of, it has tremendous adhesive properties and is not meant for things that you want to remove. The other is Lifecaulk, it is a polysulfide caulk that has good adhesive properties, which you need if the ladder is used, it will cure under water, bond wood, metal, plastic and outlasts silicone by many years if that matters. I have sealed many thru-hull transducers, hatch openings, marine door frames, etc. with Lifecaulk and have found nothing better.

[osok]

If you want a permanent water tight seal, there are two types of caulk that are better than silicone. One is 3M 5200, which is the strongest bonding caulk I know of, it has tremendous adhesive properties and is not meant for things that you want to remove.

I agree w/ transporter, this is the stuff we used exclusively when

I used to work on boats for a living. It can be removed if you really need it to be and seals and adheres like crazy.