Leaking Coaming Box

[ScubaGuy2]

I have found I have a leak from the starboard coaming box (cockpit cubby hole). Basically where the bottom of the box meets the boat is separating from the inside of the coaming slightly. This is allowing water to drip down and run along the wiring channel under the cockpit bench. I verified this is where the leak is coming from by taping kitchen plastic wrap over the box and waiting for it to rain. With the plastic wrap in place the leak is gone.

My hope is to repair this from above/outside the boat. I plan to clean and dry out the failing joint between boat and box. Then I think I have two options:
1. Slather 3M 4000 in the seam until full.
2. Slather thicken West Systems into the seam until full.

I'm unsure which would be the best option here as they both have what I think are advantages. Seems like 4000 would remain somewhat flexible if the boxes flex at all. I would think it might stick better to a less than perfectly clean surface. Epoxy would be more solid, but with no flexibility, will it separate again?

I drilled a few test holes (inside the quarter berth), I found two spots where there is some wetness in the wood core of the cockpit bench. I cut back the fiberglass and luckily found clean wood. Nothing is black or rotten looking. I plan to leave these areas open to dry out for a while before I fiberglass them back in. Oddly both of the spots I cut out had duck tape, which was holding the wires in place from the factory.

The only other thread addressing this issue I found is here:
https://forums.sailboatowners.com/index.php?threads/cockpit-pockets-separating.195940/
But unlike the photos in that post my boxes seem to be "enclosed" from below deck. When inside the quarter berth I can not see where the boxes attach to the boat (see second pic).

 

[agprice22]

Does it seem like it had a gap from the start? Or does it seem like it pulled apart over time? If the joint is not being flexed, and it was open from the start, you might try just filling the gap with adhesive. If you are flexing the joint, or it has pulled apart over time, I think adhesive may eventually pull apart, especially if there is remaining moisture on the adhered surfaces. You may want to reinforce it with a fiberglass tape and epoxy. However, I think you want a good, clean surface to work with. Thus, the fiberglass and epoxy requires more work in my opinion.
You could fill the gap with thickened epoxy filled with some fibers and use fiberglass tape on the interior corner to build a fiberglass fillet inside the box to provide both sealing and support. If the underneath is open, use a heavy tape to seal underneath to prevent epoxy from running out the bottom of your joint. Try to bond the fiberglass to either bare wood or bare fiberglass, not paint.
I have repaired and reinforced plenty of gaps like this on my boats. I choose to reinforce with fiberglass.

 

[ScubaGuy2]

Does it seem like it had a gap from the start? Or does it seem like it pulled apart over time? If the joint is not being flexed, and it was open from the start, you might try just filling the gap with adhesive.

I'm not sure. I do wonder if there was enough of a void for water to collect there. Then each year as the boat froze here in Northern Michigan the water in that void expanded and opened it up more and more. Until eventually it pulled apart enough to leak. That's just a wild guess.

If you are flexing the joint, or it has pulled apart over time, I think adhesive may eventually pull apart, especially if there is remaining moisture on the adhered surfaces. You may want to reinforce it with a fiberglass tape and epoxy. However, I think you want a good, clean surface to work with. Thus, the fiberglass and epoxy requires more work in my opinion.
You could fill the gap with thickened epoxy filled with some fibers and use fiberglass tape on the interior corner to build a fiberglass fillet inside the box to provide both sealing and support.

Thickened epoxy, then something like this? https://www.westmarine.com/buy/west-marine--fiberglass-cloth-tape--P000190001?recordNum=1

If the underneath is open, use a heavy tape to seal underneath to prevent epoxy from running out the bottom of your joint. Try to bond the fiberglass to either bare wood or bare fiberglass, not paint.
I have repaired and reinforced plenty of gaps like this on my boats. I choose to reinforce with fiberglass.

It's not open underneath.

Thanks!

 

[agprice22]

That tape would do it. You could use West Systems thickened epoxy in the tubes, but I prefer to buy epoxy and heavy or light weight filler. It is cheaper too.

 

[ScubaGuy2]

That tape would do it. You could use West Systems thickened epoxy in the tubes, but I prefer to buy epoxy and heavy or light weight filler. It is cheaper too.

I have West Systems 105, 206 & 406. Would that work?

 

[agprice22]

Yes. Sand the area to bare fiberglass or wood. Clean it with acetone. Use thickened epoxy to fill the gap. Thicken the epoxy til it does not sag off the mixing stick. Then use regular epoxy to apply the tape. Use masking tape to keep your epoxy from running and making a mess as you apply it. You can crease the tape before applying it to make it sits in the gap.

 

[Gene Neill]

I'd probably try to pour some unthickened epoxy into the crack and let it run down in deep. Wait for that to kick halfway, until it was good and tacky, then lay a fillet of thick stuff.

The products you named would be perfect.

 

[agprice22]

True. You can wet the surfaces in the gap with regular epoxy before applying the thickened epoxy.

 

[pclarksurf]

West will do it-- thicken it up -- I used 404. Probably had better than a 1/4 inch to fill along the bottom: As you mention I can't see the typical joint where the box is slapped on the side of the mold-- but certainly epoxy will fill the gap regardless of orientation.

 

[pclarksurf]

Just out of pure curiosity-- what does the cockpit side of the coaming boxes look like? Similar or different from below? :

 

[RoyS]

Recently poking around in the same area of my boat looking for a leak. My boat is different from yours. On my boat the pocket is an insert that can be removed entirely with a caulking seal on the overlapping lip. Only because I had it out and in my hand did I notice a label that said it was manufactured by "Sailing Specialties". You may be able to purchase a pocket assembly that will either fit the existing cutout or permit the cutout to be enlarged slightly to fit the new pocket. The pocket is totally waterproof inside and the lip seal is foolproof. Just a thought.

 

[ScubaGuy2]

West will do it-- thicken it up -- I used 404. Probably had better than a 1/4 inch to fill along the bottom: As you mention I can't see the typical joint where the box is slapped on the side of the mold-- but certainly epoxy will fill the gap regardless of orientation.

View attachment 166936

Oddly, this is not what mine looks like from the inside, mine is much more "intergrated" into the inside. I'm guessing this is a change made between our years. Makes no difference, just looks a bit different if you stick you head in the "coffin".

Just out of pure curiosity-- what does the cockpit side of the coaming boxes look like? Similar or different from below? :

View attachment 166947

This is what mine looks like in the cockpit.

Work is killing me, not getting much fun stuff done last couple of weeks. I should get to tackle this next week, when thing are better.

Thanks for the advice everyone, I'll post pics when I'm done.