You don't state what plastic your boat is constructed from, however I'm guessing that is either injection moulded or vac formed, both of which generally use plastics that don't respond well to laquer based paints i.e. cellulose based.
Cellulose based paints will melt most thermoformed plastics, but won't damage thermoset plastics like polyester, polyurethane and epoxy based resins.
Acrylic paints or oil based enamels are a good choice for thermoplastics, they won't damage the hull. Don't use acrylics on top of enamels.
You can also coat your model in an acrylic based primer whereupon you can freely use cellulose based products, as this acts as a shield beteen the paint and plastic.
Stores that supply car paint represent a cheap source of paint, and you can generally get it mixed to any shade you require. The disadvantage of this approach is that you usually have to purchase a minimum quantity (usually 1/2 litre) which can workout expensive in the short term.
BTW the latest Sub Com report had two excellent articles explaining how to paint your boat!
Edited By Sub culture on 1088067220