Which caulk to use

Radiowave

Radiowave

Member
Sep 30, 2012
46
Edgewater, Maryland
Boat Info
2009 330 Sundancer
Engines
496 Mercruiser w/Bravo III drives
I noticed a leak inside the boat at the port side skylight. What is the recommended caulk product for this job? My plan is to remove both skylights carefully, clean them as well as the entire area where they sit and set the glass back and fill in the area. Is the job more involved than that?
 
I replaced the acrylic in our hatch a few years ago using Dow Corning 795 sealant. Great product, easy to use, easy to trim afterward with razor blade. Also used it to seal around leaking aluminum frame to fiberglass joint on aft cabin window.
 
3m 5200 is great marine sealant can find at Home Depot. This stuff will cure under water and will not dry and crack.
 
Radiowave said:
I noticed a leak inside the boat at the port side skylight. What is the recommended caulk product for this job? My plan is to remove both skylights carefully, clean them as well as the entire area where they sit and set the glass back and fill in the area. Is the job more involved than that?
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I wouldn’t use 5200 for that. It’s damn near permanent. If you don’t get it right and it leaks again you’re destroy the boat getting it off. 4000UV is a good sealant for that.
 
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340 Ray said:
3m 5200 is great marine sealant can find at Home Depot. This stuff will cure under water and will not dry and crack.
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5200 is an adhesive that is a permanent bond ,you wouldn’t want to use that on the hatch . 4200 is what I would use in case you ever need to remove or re-bed the hatch
 
Searay beds these with 100% silicone. I talked to them and had this discussion. If it were me I would remove it completely and clean the old caulking with DeBond. Make sure any entry into the voting is sealed with epoxy resin, then tape off the surrounding area with painters tape and reinstall. Any brand would work, personally I am using 3m marine silicone because it cost more so it must be much better (totally joking here but that is what I’m using)
 
As said don't use 5200 or you will destroy the skylights if you try to remove them again in the future.
 
Your best bet is to remove the skylight(heat or however) and make a larger skylight that sits higher. On the ‘09’s is a triangle design if I’m not mistaken but most shops could do it. It’s simply a bad design that lets water pool. The silicone adhesive used cracks, fades, wears away over time so make sure you put an adequate bead down of a quality waterproof sealant.

I will add Dow 795 is a great product. Used that on mine. Seal and flexes. If you have any questions take a look at Boatworks Today on YouTube. That guy is great at this sort of thing and explains and shows the details of how to do it.
 
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Tiara uses 4200 on hatches and port lights. Owned my 3200 for 16 years and it never leaked anywhere. First boat I've owned that never ever leaked. I would use 4200 on your hatches.
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Not to hijack the thread (but apparently I will anyway) what is the best product to use on the rub rail?
 
JPGator said:
What wrong with the rub rail, let’s start there?
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Nothing...the prior/exisiting caulking is just pulled out/missing in some spots. For now I'm just going to pull the rest out and re-caulk in place. Eventually I will pull the rail and re-bed it.
 
I’m still a fan of the 4000UV. Does a good job and lasts. If you haven’t tackled this before just take your time and clean everything out. A little painters tape on the top and bottom can also save you some time with any extra caulking that comes out.
 
Agree with everyone, definitely do not use 5200.

I guess I'm the odd ball. Post shipping, I had to put my flybridge back together. The windscreen was a PIA to caulk, and then I had to caulk around all of the railing bases and around the radar arch. I looked at "marine silicone" sealant at $30 a tube at WM, then walked next door to Home Depot. Found their waterproof silicone bathroom sealant looked to be the same at $6, so bought a couple of tubes of it. Looks great, and no issues to date as I wash with a direct stream.

Regardless, tape off both sides of where you need the sealant, that's how you end up with a straight, clean look. Apply the sealant where the two surfaces meet, then use your finger to both compact and smooth the surface. I let mine cure for a couple of days, then peeled off the tape - and it looked like it was done at the factory.

The key ingredients are prep and taping...

Our Meridian Caulk.jpg
 
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