Leaking through hull - seal or let leak

[Mazamou]

Hi Guys,

New to the forum and have question which has probably been asked before, but maybe not in the same context 😊

My through hull transducer is leaking, nothing drastic, a cup of water every day. Whoever installed it has gone straight through the hull and not set it in casting resin. I intend to pull it out and repair but not straight away as I only just put the boat back in the water 😭

Now here is the question....I have managed to seal the leak on the inside but now I'm thinking the water would be getting forced into the core. Should I unseal and let the water continue to leak to the inside of the boat or leave it sealed.. thoughts?

The boat is a 40ft fibreglass (foam core) and permanently based in the marina, salt water.

Appreciate your advice.

[paulajayne]

Lift it out and do the job correctly. It will get worse the longer you leave it.

[Mazamou]

Thanks for the reply, that is the obvious solution... In my situation I can't lift it out immediately. It needs to wait another 2 weeks. So my question is "would you let it leak through to the inside or seal it?"

[paulajayne]

Sealing it will increase the pressure of water on the core so I would let it leak but monitor it closely. Bilge pump on auto.

Once out remove fitting and check the core - giving it chance to dry.

[Mazamou]

Cheers Paulajayne.... That was my thoughts, I will remove the seal in the morning.
Once I lift it, I will hole saw a larger diameter taking out some of the soaked core, then let it dry and refill with resin before drilling out to refit.

[marcjsmith]

i would not cut a larger diameter hole in the skin(inner or outer) first excise out the bad core to see how deep it goes. if its not too deep say an inch or so then you can possibly refill the missing core area with epoxy/resin/cabocil, etc without affecting the skin layers. and create a suitable bed for the transducer and also protect the existing foam from potential damage from a future leak bay far the easiest option..



if the damaged core is too deep to excise easily then I would cut back the interior skin and do a proper foam core repair from the inside, then properly install the transducer after prepping the hole for the transducer.


Keep in mind that if you end up removing the inner skin to make a core repair. since you are below the water line it would be a structural repair. the proper process would be cut a bevel/tapered edge in the old and new core material so you have an overlap with no hard edges and then reskin the area with new glass extending beyond the repaired areas... that's the cliff notes version.


hopefully its the easy repair option...


take pics and post...

[Avionics_Joe]

When you pull it you might want to consider vacuum bagging the area to boil off the water in the core.

If its cold where you are this might not be a good idea as the vacuum boil off can cause the water to freeze.

Good luck,

Joe

[Mazamou]

Marcjsmith, thanks for the advice... I like the idea of digging out some of the core and to replace with resin. I'm hoping the damage has not spread too far.

My plan was to hole saw out the inner skin to a wider diameter, and remove the core. Then fill with resin, see attached which is airmar recommendations.

At the moment the through hull hole is only 2 to 5 mm wider than the transducer, wth no resin. Will post some pics tomorrow.

[Sun and Moon]

Ummm... Have you read "If you give a mouse a cookie"?

Why assume that the core is saturated and needs repair before verifying that?
If the transducer was installed correctly, a larger hole was cut out and then sealed. A leaking transducer will not cause damage other than the water in the bilge. Likely, all that needs to be done is remove and rebed the transducer. There is no rush to do this, other than considering whether the leak is likely to become more serious with time.

Even if some yahoo installed the transducer leaving the core exposed, the damage is already being done. Waiting another two weeks to pull isn't going to significantly change the situation. And the core may not be damaged yet - merely wet and needing to be dried. Do you have any idea how long it has been leaking for?

And if this was my boat, next time I hauled out I would consider removing the transducer, glassing over the hole and reinstalling a through-hull transducer that can't leak. But that's just me not liking holes in my boat.

[Mazamou]

I'm guessing it's been leaking for close to 6 months, as there was no water prior to putting it back in the water in August. And the water I found months ago I thought was coming from the generator.

Definitely no resin. I removed my temp seal put in 2 days ago to allow water back through thus not forcing it into the core. Like I said the water coming through is minimal.

Few photos attached.

[wholybee]

I don't think having sealant on the inside of the boat will make any difference to the core. It is underwater and not sealed on the outside, water is getting in there. Having a seal on the inside will not "force" it into the core. The water pressure into the core is determined by how deep under water it is, and an inside seal doesn't change that.

It looks like someone just drilled a hole and stuck the through hull in it. That is not right. A backing plate should be fiberglassed on the inside to strengthen the area. I would add the backing plate after you do the work you describe in post 8 above.

[paulajayne]

"The water pressure into the core is determined by how deep under water it is, and an inside seal doesn't change that."

Not quite correct.

Sealing the inside will leave the core exposed to the standing pressure of the depth of water, not sealing it will allow a small pressure drop as the inside pressure is lower.
Not a great deal of difference but will help slightly.

[Dockhead]

Originally Posted by Mazamou

Hi Guys,

New to the forum and have question which has probably been asked before, but maybe not in the same context ��

My through hull transducer is leaking, nothing drastic, a cup of water every day. Whoever installed it has gone straight through the hull and not set it in casting resin. I intend to pull it out and repair but not straight away as I only just put the boat back in the water ��

Now here is the question....I have managed to seal the leak on the inside but now I'm thinking the water would be getting forced into the core. Should I unseal and let the water continue to leak to the inside of the boat or leave it sealed.. thoughts?

The boat is a 40ft fibreglass (foam core) and permanently based in the marina, salt water.

Appreciate your advice.

I hate to be the bearer of bad news, but depending on the type of foam used -- there are many different types with very different propensities to absorb water -- your hull could already be irretrievably destroyed.

I've been there and done that, with a day sailer I owned as a teenager -- tiny crack in the centerboard trunk resulted in completely saturated foam core repairable only by cutting the hull in two and replacing all the foam -- it was a total loss. I sold the rig and gear and landfilled the hull.

With luck you will have a better grade of foam, through which water doesn't propagate as quickly. And if your core was vacuum bagged -- some very high quality cored hulls are built this way -- then you probably won't have a big problem. But if I were you, I would lift out without delay and investigate, as the damage will spread with every day.

I would sue whoever did that heinous job if I could find the person, if I were you. Cored Hulls 101 is of course never ever do something like that. My present boat has a cored hull -- which is much stronger and much lighter, I wouldn't have it any other way -- but I would never add holes outside of the designated areas, which are areas of solid uncored glass specially made for through hulls. It is possible to put a new hole through a cored section of the hull, but it has to be done with extreme caution by a person with top skills.

[Mazamou]

I believe water will take the path of least resistance... if the hull is sealed inside then water is going to want to travel into the foam core. If unsealed the water will travel past the core and into the boat, obviously some water still finding its way into the core. So I still agree with paulajayne

The depth is approximately <500mm.

Anyway... it's unsealed now and what little water is finding its way in is being thrown out by the bilge. Will lift her out in a couple of weeks and assess the damage.

Will post some pictures and update with a damage report. And will definitely install a decent backing plate thanks wholybee.

[Mazamou]

Hopefully your wrong Dockhead and its good quality foam and the water has struggled to penetrate more than a few inches... wishful thinking I know.

I intend to lift her out as soon as I can and the job will be done correctly. Will take the opportunity to update the transducer at the same time. Might even glass over and switch to a in-hull 😆