Murphy's law

[CDK]

When closing old cut-outs and attaching stern tubes to the transom, I must have overseen something. After a 5 month's refurbishing job (from gasoline to diesel, from jets to tunnel drives) the boat went back into the water yesterday. Despite numerous layers of glass and copious amounts of resin plus 2 layer of anti-fouling, a trickle of water slowly fills the bilge until the pump switches on.
Murphy's law, applied to liquids, says that a 1" drain will clog up within days when left unattended, but a pinhole will leak forever....

For various reasons, taking the boat out again is presently no option. Is there a product or procedure to stop a small leak from inside or outside in a submerged location?

[charmc]

Marine polyurethane sealants will cure underwater. 3M 5200 is one example. Polysulfide sealants will work well for underwater service, and there are products made specifically for underwater leak repair.

There is a company that willl take international orders and can ship anywhere. Their site has a lot of information on underwater leak repair products and techniques

http://www.epoxyproducts.com/marine.html

There will be others here with first hand experience and more knowledge, but this should be a good start. It sounds like you've done a huge amount of work, soon you can move to the enjoyment phase.

Good luck!

[RHough]

When closing old cut-outs and attaching stern tubes to the transom, I must have overseen something. After a 5 month's refurbishing job (from gasoline to diesel, from jets to tunnel drives) the boat went back into the water yesterday. Despite numerous layers of glass and copious amounts of resin plus 2 layer of anti-fouling, a trickle of water slowly fills the bilge until the pump switches on.
Murphy's law, applied to liquids, says that a 1" drain will clog up within days when left unattended, but a pinhole will leak forever....

For various reasons, taking the boat out again is presently no option. Is there a product or procedure to stop a small leak from inside or outside in a submerged location?

Unless you can locate the source on the outside of the hull, plugging the leak from inside will be a mistake. All the structure and laminates will become waterlogged.

If you can find the entry point and plug/seal it from the exterior of the hull you might be able to prevent the leak from undoing all your work.

Pulling the boat out and fixing it right will save money and time in the long run.

[CDK]

Would it be an option to enlarge the leak with a drill so the snout of a sealant gun fits and then pump sealant in it? The water should be pushed back by the sealant, which should be a type that is sticky enough to adhere to a wet surface.

[Frosty]

You should find the leak. it may just be a mechanical leak from shaft or hose or something. Thinking it may be coming in from the numerous fibre glass laminates is ,, frankly a bit frightening.

[Landlubber]

CDK,

I am afraid that Frosty and others are right, there is only one way to do it, pull the boat and do the job correctly, it is always cheaper to do the job right the first time. The poor man pays twice.

[CDK]

As I wrote in the first post, getting the boat out is no option. The trailer has suffered so much damage from exposure to salt that it is no longer fit for duty and never will be, the slip is taken by a fisher for the next few months and my boat can only float. There is still a lot of electric wiring to do and some parts to be made. I will need at least another 6 weeks until the first test run.

The leak comes from where bottom and transom meet. There was an 8x20" hole in the bottom where the jet intake was and a large opening in the transom for the pump body. I closed both with glass and resin in several stages, starting with the bottom. The prop shafts are in oil filled stainless tubes with neoprene seals, they are no suspects. They are bolted to the transom with 10x12" flanges against which I laminated more than 1" wall thickness, used a wood core and laminated another 1/4".
I think that the problem is in a sharp corner where the glass fiber didn't reach deep enough.

[RHough]

The leak comes from where bottom and transom meet. There was an 8x20" hole in the bottom where the jet intake was and a large opening in the transom for the pump body. I closed both with glass and resin in several stages, starting with the bottom. The prop shafts are in oil filled stainless tubes with neoprene seals, they are no suspects. They are bolted to the transom with 10x12" flanges against which I laminated more than 1" wall thickness, used a wood core and laminated another 1/4".
I think that the problem is in a sharp corner where the glass fiber didn't reach deep enough.

It is not going to get better, it might very well get worse. Any leak such as you describe is probably hard at work undoing as much of your work as it can. Patching the leak from the inside will only slow the rate of the damage.

There shouldn't be a 'sharp corner' in the glass at the transom *inside* the boat. The glass on the outside of the transom/hull should be laid up on a radius too, then an edge created for planing hulls. AKAIK sharp corners and glass are a bad combo.

There must be another option. What is the tidal range? Could you careen the boat to see where the water leaks *out*? That might help find the source. After the source cause is known, you can plan a repair and try to come up with a way to do it in stages that allow you to work the low tide window.

Is there a crane? Can you borrow a trailer for a few days?

There are all sorts of options that sound better to me than trying an in the water fix from inside the boat.

[charmc]

RHough and landlubber are right; the best solution is to get the transom out of water and make a permanent repair. If you are absolutely, absolutely positive that there is no way to do this you will need to do the mask and snorkel or SCUBA thing and seal it from the outside. Water has worn away mountains because it is unrelenting. If you inject from the outside, water pressure will help make the seal. Attempt it from the inside while the boat is in the water and the small amount of water pressure will be your unrelenting enemy, working against the repair and migrating by capillary movement into your laminate.

Pool supply stores sell a red dye which will help spot a leak. Squirt some at points along the transom a few inches/cm away. You will be able to see it move slowly to the point of the leak. Mark the spot and use the sealant from the outside. The contents of dye markers, vegetable coloring, or red beet juice might work if you can't find the specific leak checking product. If the water is murky, use a light and stay close.

Once you're able to haul her out, redoing fiberglass with a radius as described above will make a permanent repair.

This small but important step will preserve the results of all your hard work. Don't let it ruin the great job you've done already. Good luck!

[PAR]

A typical issue with larger craft and easily addressed with counter flooding, or a better choice in your case is weighting the bow. I'm not sure of the boat you're working on (I'm assuming it's the Draco), but sometimes you just don't have an option to haul her out (as in your case). Though getting her on the hard is ideal, from several vantage points, stopping flow and stemming the leak is the first order of business.

On vessels under say 35' LOD, you'll likely be best suited with a few 55 gallon drums on the fore deck. The plastic ones are reasonably easy on surfaces and available enough. Fill them one at a time until your areas of question are clear.

Personally I'd find the leak. Even a pin hole will leave a trail, however convoluted it may be. With this area in mind, trim her down by the bow until this area is clear and pump her dry.

Another option is to "bag" her. Floatation bags can be tied to her butt and inflated to hoist the stern clear.

Epoxy would be my first choice to temporarily seal the leak. Several brands have dough like epoxies that will cure underwater and are ideal in this situation, but you have to know where to put it.

I'm betting on something other then a pin hole or delaminated area. Check the rudder port(s), stuffing box(s), thru hull(s), etc. and generally eliminate all the obvious places. Once this is completed, you're left with the probably of a pin hole or some sort of delamination or poor layup.

[Frosty]

This repair sounds to be as serious of a job as the modification was in the first place. You just cant have water seeping in through the laminates. Sorry but this must be a terrible job and needs doing again.

[CDK]

"Pool supply stores sell a red dye which will help spot a leak. Squirt some at points along the transom a few inches/cm away. You will be able to see it move slowly to the point of the leak. Mark the spot and use the sealant from the outside. The contents of dye markers, vegetable coloring, or red beet juice might work if you can't find the specific leak checking product. If the water is murky, use a light and stay close."

Using a dye marker to locate a leak is next to impossible; the sea is never at rest and spreads the dye immediately.
The best suggestion came from my wife (!). She said "why don't you use compressed air?" So next time before posting questions on the forum, I will humbly ask her opinion first.
Anyhow, the entry point has been located. The stainless flange was bolted to the transom at 4 corners first to cover the old jet cut-out. Then I built up GRP layers against it to close the transom. To be able to pull the flange tight to the laminate I used paper tape around the bolts. Near one of the bolts water gets behind the flange and found a way in.

[KnottyBuoyz]

HI CDK

Like you I'm an experimental engineer! Anyhow, your wife was onto something. Instead of compressed air why not try a vacuum! If you can get the boat high and dry you can place an airtight bag (plastic film) over the transom where you've made the modifications. Once you've done that draw down a vacuum on the bag to draw out any air. From there you'll be able to apply epoxy resin on the inside and the vacuum will draw it through the voids to seal the leak. There's plenty of resources on the web on vacuum resin infusion this is just a small tweak on that process.

Just a thought.

Rick

[CDK]

The matter has been taken care of.
I've used a metal construction to lift the boat and had some help from the tide as well. Once dry, the place where the water entered was of course invisible again: you can't see air bubbles in air....
After cleaning and degreasing I coated the relevant transom area with Sikaflex-291 marine sealant using a putty knife and the next day gave it another coat of anti-fouling.
She is now back in the water again for almost a week with no signs of leakage.