"Cornelis Koger" wrote:

My Draco 2500 twincab has been repowered with VW td engines and tunnel
drives of my own design, for which I have added a 1 ft long box to the
stern. In fact it is an extension of the hull that supports the 2 tunnels,
rudders etc.
Although I've spent many hours on my back under the hull laminating and
painting, now that the boat is back in the water, a steady trickle of
water is entering the bilge through one of the holes where the stern tube
is bolted to the stern. The bolts are not visible outside, they are in a
grp walled cavity filled with polyurethane foam.
I would have bet anything that the construction is watertight, but I'm
glad I didn't.

My plan is to locate the hole by pressing a sponge soaked in dye against
the suspected area, with a helper inside who looks for a color change of
the incoming water.

Is anyone familiar with a product or procedure that can successfully seal
a small hole in a submerged object?

Steve Lusardi wrote:

Perhaps your dilemma is far worse than you suspect. If you have a leak into
a foamed area and that foam is not closed cell, you have foam that will be
waterlogged. If also in that same cavity you have end grain glass exposed,
you will also suffer osmosis. I am afraid you have a winter project redoing
the entire area. The cost of NOT doing that will be far worse.
Steve

Haul out, rip out stern tube, remove waterlogged foam and dry out, grind
back to sound GRP, replace the bonded in nuts. laminate up a GRP tube to
sleeve the stern tube, bond in place checking alignment carefully, fair
and make good. When fully cured, bed the stern tube and its end
fittings in with plenty of a good quality sealant. (Assuming metal stern
tube, a GRP one gets glassed in directly.) There is NO shortcut. OTOH
the leak could be anywhere along the joint of the hull extension so you
may have an even bigger job as if its leaking at the joint, the
structural integrity of the whole addition is questionable.

If foam wasn't involved you *might* have been able to bodge it with
epoxy putty applied underwater. The dye isn't going to be any use as
the volume of water allready in the foam will dilute it to the point
that you dont get a clear colour change in anything like a reasonable
time to keep the sponge in place.

Been there myself and spent a winter on the hard fixing it right.