How to hunt down hull seam leaks?

[limbodog]

1985 Hunter 40.

So this seems like it could be my biggest issue. Everything else I can get my head around what to do about it, but this one has me worried.

I see 4 places where water comes in when it rains. All of them are in the aft cabin.

#1 drip is coming in on the starboard side, dripping down the fuzzy (what the hell is that material anyway?) siding of the interior hull and pooling on the shelf beside the bed. The wood there is rotted and growing flora. It's a couple inches away from one of the electrical outlets too, which concerns me.

#2 drip is also on the starboard hull coming in right where the the topside deck ends and the transom storage begins.

#3 drip is the same as #2, but on the port side.

#4 drip is pouring out of the fuzzy material separating the ceiling of the rear cabin from the aft compartment housing the diesel tank and rudder assembly.

What I conclude from all of this is that any water above deck is either coming in through the scuppers and finding its way into the ceiling, or coming in through the hull seem, traveling backwards, and eventually finding the lowest point in the fiberglass to leak through.

So basically I have 80' of seem in which to find 2 leaks, and also the scuppers and pedestal seal to check.

I've got some of that "Captain Tolley's Penetrating Glue" in the hopes that I can drip it into every crevice I see and hopefully if I do that enough the leaks will be plugged eventually.

Help? Is there a way to do this other than disassembling the entire hull, scraping out the joint, and re-sealing it?

(can post a pic or two tonight if needed)

 

[Don S/V ILLusion]

Not practicalthis time of year in Boston but use a hose on deck on one discrete area at a time, e.g., cleat, rubrail section, seam, etc... to pinpoint source(s) of you leaks.
Finding a leak is usually easier than eliminating the resultant mold behind often immovable bulkheads and structural members.

 

[LeslieTroyer]

Pressurize the boat with a box or squirrel fan in the companion way. Use tubing in on ear and the other running along the seam in question (or steal a dr/mechanics stethoscope)

 

[DayDreamer41]

Pressurize the boat with a box or squirrel fan in the companion way. Use tubing in on ear and the other running along the seam in question (or steal a dr/mechanics stethoscope)

Once the cabin is pressurized could one not use a soapy water spray and watch for bubbles? A leaf blower might be another option to pressurize the cabin as well, and here on SBO's we don't recommend theft as a means of acquiring items needed.....

 

[limbodog]

You can hear the leak over the fan? Even with a stethoscope I would think the noise would be too great. But that seems doable. (My NP friend likely has a stethoscope she can loan me)

And yeah, I guess when it's not 20ºf out, I could just set up the hose on the gunwales and slowly move it around until the water started to pour in.

Anyone have thoughts on that penetrating glue stuff?

 

[BlowMeAway]

Once the cabin is pressurized could one not use a soapy water spray and watch for bubbles? A leaf blower might be another option to pressurize the cabin as well, and here on SBO's we don't recommend theft as a means of acquiring items needed.....

On the soapy water and leaf blower. Just assure all port lights, hatches are closed and seal up the companionway with cardboard or heavy weight plastic sheeting. Use a soft brush and a bucket full of soapy water (Dawn dish detergent works great). Apply liberally to all areas on deck seams and hardware...look for bubbles. You’ll find the leaks...and have a slightly cleaner boat if you rinse.

 

[limbodog]

That I like better than just pouring water into the leaks. I mean, sure, I'm still pouring *some* water, but maybe less so. I'll have to see how effectively I can seal off the boat tho'. Some of my hatches are held shut mostly by gravity and willpower and might prevent the pressurization. Probably something to do when it's not cold out too.

 

[Boomer54]

Anyone have thoughts on that penetrating glue stuff?

Yes. I have used Captain Tolleys. It essentially is an epoxy type glue but much less viscous so it flows and finds its way into essentially hairline cracks. For that type of issue, it works well. But first, you need to find your leaks and I’d guess they may be due to “cracks” which are better sealed with 4200 or some similar thing. I’d cover it well for the winter and work on finding the leaks in the spring.

 

[Terry Cox]

1985 Hunter 40.

Different model here, but had a similar problem in our boat. Odds are wherever there is a fixture attached to the deck, that becomes a leak source. A bright flashlight and magnifying glass helps to observe where sealant has either worn away or opened up. That is what I did and now our boat is leak free.

In our aft cabin one leak source was a port light bedding had opened up/worn away. So I applied a high quality sealant around where the frame lays against the deck. Leak stopped. Another was rain water entering our cockpit arch sound box. Water would follow the wires into and down the arch tubing into the aft cabin. After placing a drip loop in the wires before they entered the arch allowed the rain water to exit the wire chase before entering the arch tubing. Leak stopped.

Forward cabin hatch was leaking rain water. Still leaked after applying sealant around the hatch frame. Noticed during inspection of the big port light in the main cabin that some parts of the old sealant had opened up/worn away. Applied new sealant and leak stopped.

 

[FastOlson]

On the soapy water and leaf blower. Just assure all port lights, hatches are closed and seal up the companionway with cardboard or heavy weight plastic sheeting. Use a soft brush and a bucket full of soapy water (Dawn dish detergent works great). Apply liberally to all areas on deck seams and hardware...look for bubbles. You’ll find the leaks...and have a slightly cleaner boat if you rinse.

I was invited to watch this method used on a 34 footer and it does work. You will use a lot of blue tape to cover all of the places where air will leak out... and do not forget the cockpit seats and vents.
Use a big shop vac. Put a three inch hole in a temporary 1/4 inch hatch board.
The bubbles do indeed show up when the soap is sprayed on... and probably in places you had not considered previously.

 

[limbodog]

Cool! Will be doing exactly that

 

[Will Gilmore]

When you do. Pictures would be awesome.
I wish you success.

-Will (Dragonfly)

 

[limbodog]

I'm taking lots of pics & vids on most of my projects. But I am a terrible photographer/videographer.

 

[jssailem]

@limbodog, you will improve your picture taking by practice. Take them and post them here. They really help to explain what you mean by, “drippingdown the fuzzy (what the hell is that material anyway?“

Drips can be a mystery. While it is possible that a side seam has fractured (there would be damage evidence to the side of the boat) and may be the cause of your leaks it is more likely what @Terry Cox suggested. The things on your deck or cracks at the corners of fittings have created a path for water intrusion. Once inside water will follow the path of least resistance and can appear in a place seemingly unrelated to the source. The forced air inflation and soapy water idea is a great trick when you feel desperate.

I would look to anything with a screw hole in the deck near the area of your 4 leaks as the best place to start. Likely the fitting (be it a winch, a cleat, or a stanchion etc.) has been stressed and the bedding has cracked opening a path for water intrusion. Taking the fitting off to be rebedded may give you one of those “Ah Haaa that is the bugger causing my problems!” moments.

Unfortunately this sounds like a task best started next spring. So breakout the pots and pans and capture the leaks till the sunny spring days return, unless it is Sunday and you can escape Boston for a warmer, gentler Latitude..

 

[limbodog]

Yeah, after reading @Terry Cox 's post I'm rethinking the sources. I'll be taking a look at every deck fitting over time. I think I've got some likely candidates to start with tho' as they look most likely to lead to where I'm seeing the water come in.

I am still waiting on my clear shrink-wrapping job. Was supposed to be a couple weeks ago, but I'm learning that nothing is ever on time. I suspect that any re-bedding of a fitting has to wait until spring for warmer temperatures, but is there any reason to wait until then to remove suspect hardware once I'm under cover?

 

[Terry Cox]

is there any reason to wait until then to remove suspect hardware once I'm under cover?

Unable to think of a reason. Good time to take on that task. Some might have a different thought, but 3M-4200 for above the waterline sealant, has always worked well for me. Never used Silicone II around the boat. Really dislike that stuff. PO used it some without solving the problem and what a mess to clean up.

 

[limbodog]

I see that the debates over which VOCs to use for deck sealing are vast and varied. I was leaning towards butyl tape, but honestly it's mostly because of Sail Life Youtube guy https://www.youtube.com/user/madsdahlke

 

[jssailem]

@limbodog I can understand the attraction this guy does have an interesting voice.

I found the professional background of MaineSail on MarineHowTo.com and the detail he provides to support his claims, worthy of testing the products.
Then there are the supporting professional recommendations and finally the actual experience testing the product that one me over to the use of Butyl Tape as the tool on my boat for bedding hardware.

Yet the beauty of this boat world is we own the boat and we get to make the decision.