depensd on what is on their already and what your planning on putting on, some paints react with each other or don\'t adhere very well, If its still in gel coat, might be better to spend time repolishing or applying a new gel coat, unless its a complete colour change your after. Good rub down, then do it again just in case, more time pent preparing the surface the better the end resultt. Probably be worth while investing in a coat of barrs primer/isolator or a UCP isolator primer first, this will give a good barrier between old and new so there won\'t be a reaction and give a good key for top coat. Gonna cost more in time than money if you want a nice shiny boat at the end