Not a lot of info there, is it wood? Fibreglass? Plastic? Does the whole hull need sealing / painting? Or do you have splits? Or water coming in somewhere? What type of boat is it?
I'm sure we can help when we understand the issues.
I found some stuff in B&Q called "Diall", an own brand paint remover. Kinder to plastic than Nitromors (at least, the Nitromors that I remember). While the hull is ply, there might always be some plastic bits lurking under the paint.