To fix the leaks in worn hypalon and PVC inflatable boat fabric use Polymarine Sealflex. It is a very flexible and high tensile film sealant. Ideal for use with inflatables which have worn and become porous with tiny pinholes.
Sealflex is an air curing water based acrylic sealant forming a very flexible and high tensile film, which when fully cured seals off minor leaks and porous fabrics by creating an air barrier on the inside of inflatables.
The method of repair is simple. Having first identified the problem areas, introduce the Sealflex through the inflation valve (using a small funnel if necessary), dividing the material between the chambers. Inflate to as high pressure as possible and roll the inflatable to distribute the liquid, paying particular attention to the problem areas identified. The air pressure will force the sealant into fabric creating an air barrier. Pour out any excess continuing to roll the boat from time to time to recirculate any remaining liquid. Sealflex is air curing so over the next few days partially deflate and re inflate to assist in the curing process.