This weekend I finished painting my Chesepeake (below waterline) with a single component silicone alkyd enamel marine paint. Following the 3rd coat I find the paint very delicate - scratches very easily and in some areas where the paint is a bit too thick it seems soft. Would a linear polyurethane clearcoat or varnish polyurethane strengthen the paint and make it stronger when sliding on a vehicle roof rack or dragging on shores? Will this paint harden any more as time passes? Thanks.