Osmosis or boat rot is a funny old thing. There are many expensive cures and remedies. Although some would say the simplest and least expensive are just as worthy. I suppose it would depend on a number of factors.

An effective repair used to good effect involved the use of thinners, a paint of either polyurethane or epoxy and bath type sealant. This was particularly effective with delamination in awkward places to the fibreglass that would otherwise entail too much cutting away. The use of paint colours to match has obvious advantages. The first step is to evaluate the extent of the damage. There would be little advantage in creating unnecessary work.

From the inside of the craft, or with the surface to be repaired laid so that the fluid may find its way by seepage, drill a few small holes round the surrounding damage. Not enough to penetrate the hull, but deep enough to go through the area of damage.

There are a number of proprietary thinners that will not attack the fibreglass and dependant on the type of paint used. If this is allowed to soak in and penetrate, then followed by very thinned out paint in less diluted layers between drying, a good effect may be observed. The seepage and hardening process filters through the area of damage. Epoxy or polyurethane, depending on what part of the boat has seen good effect.

For those areas inside the hull where delamination can be cavernous, the use of bath sealant injected into the spaces through the drilled holes and then wiped smooth with the surface gives a pleasing effect once it has hardened out. This will also prevent later ingress of water that initially caused the damage.

This repair may not be to everyone’s liking, but a DIY repair is far more preferable than gouging out great areas that may cause more concern and unnecessary time and expense. The reality of repair for its own sake is the main consideration.